xo-alloc2: + guard bytes at beginning of arena + refactoring
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8 changed files with 210 additions and 89 deletions
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@ -8,6 +8,7 @@
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#include "xo/indentlog/scope.hpp"
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#include <cassert>
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#include <cstddef>
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#include <cstring>
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#include <sys/mman.h>
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namespace xo {
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@ -77,12 +78,6 @@ namespace xo {
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s.last_error_ = AllocatorError(error::reserve_exhausted,
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s.error_count_,
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target_z, s.committed_z_, reserved(s));
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#ifdef OBSOLETE
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throw std::runtime_error(tostr("ArenaAlloc::expand: requested size exceeds reserved size",
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xtag("requested", target_z),
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xtag("reserved", reserved(s))));
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#endif
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return false;
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}
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@ -114,13 +109,15 @@ namespace xo {
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// log && log(xtag("aligned_offset_z", aligned_offset_z),
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// xtag("add_commit_z", add_commit_z));
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// log && log("expand committed range",
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// xtag("commit_start", commit_start),
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// xtag("add_commit_z", add_commit_z),
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// xtag("commit_end", commit_start + add_commit_z));
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if (::mprotect(commit_start, add_commit_z, PROT_READ | PROT_WRITE) != 0) [[unlikely]] {
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if (::mprotect(commit_start,
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add_commit_z,
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PROT_READ | PROT_WRITE) != 0) [[unlikely]]
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{
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++(s.error_count_);
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s.last_error_ = AllocatorError(error::commit_failed,
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s.error_count_,
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@ -136,11 +133,22 @@ namespace xo {
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s.committed_z_ = aligned_target_z;
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s.limit_ = s.lo_ + s.committed_z_;
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if (commit_start == s.lo_) [[unlikely]]
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{
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/* first expand() for this allocator - start with guard_z_ bytes */
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::memset(s.free_,
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s.config_.guard_byte_,
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s.config_.guard_z_);
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s.free_ += s.config_.guard_z_;
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}
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assert(s.committed_z_ % s.config_.hugepage_z_ == 0);
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assert(reinterpret_cast<size_t>(s.limit_) % s.config_.hugepage_z_ == 0);
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return true;
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}
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} /*expand*/
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std::byte *
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IAllocator_DArena::alloc(DArena & s,
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@ -165,8 +173,6 @@ namespace xo {
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* ArenaConfig.store_header_flag_ disabled
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*/
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bool remember_header_flag = s.config_.store_header_flag_;
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return _alloc(s, req_z,
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alloc_mode::super);
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}
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@ -258,17 +264,37 @@ namespace xo {
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#endif
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}
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std::byte *
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byte *
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IAllocator_DArena::_alloc(DArena & s,
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std::size_t req_z,
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bool store_header_flag,
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bool remember_header_flag)
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alloc_mode mode)
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{
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scope log(XO_DEBUG(s.config_.debug_flag_));
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/*
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* sub_complete
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* sub_incomplete |
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* standard super | |
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* v v v v
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*/
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std::array<bool, 4> store_header_v = {{ true, true, false, false }};
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std::array<bool, 4> retain_header_v = {{ false, true, false, false }};
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std::array<bool, 4> store_guard_v = {{ true, false, false, true }};
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/* -> write header at s.free_ */
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bool store_header_flag = false;
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/* -> stash s.last_header_*/
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bool retain_header_flag = false;
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/* -> write guard bytes */
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bool store_guard = false;
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if (s.config_.store_header_flag_) {
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store_header_flag = store_header_v[(int)mode];
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retain_header_flag = retain_header_v[(int)mode];
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store_guard = store_guard_v[(int)mode];
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}
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assert(padding::is_aligned((size_t)s.free_));
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/* remember_header_flag -implies-> store_header_flag */
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assert(store_header_flag || !remember_header_flag);
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/*
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* free_(pre)
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@ -277,7 +303,7 @@ namespace xo {
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* <-------------z1--------------->
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* < guard >< hz >< req_z >< dz >< guard >
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*
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* used <== +++++++++0000zzzz@@@@@@@@@@@@@@@@@ppppppp+++++++++ ==> unallocated
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* used <== +++++++++0000zzzz@@@@@@@@@@@@@@@@@ppppppp+++++++++ ==> avail
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*
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* ^ ^ ^
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* header mem |
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@ -296,12 +322,15 @@ namespace xo {
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/* dz: pad req_z to alignment size (multiple of 8 bytes, probably) */
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size_t dz = padding::alloc_padding(req_z);
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size_t z0 = req_z + dz;
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/* if non-zero: will store padded alloc size at the beginning of each allocation
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* reminder: important to store padded size for correct arena iteration
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/* if non-zero:
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* will store padded alloc size at the beginning of each allocation
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* reminder:
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* important to store padded size for correct arena iteration
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*/
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uint64_t header = req_z + dz;
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if (store_header_flag) {
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if (store_header_flag)
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{
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if ((s.config_.header_size_mask_ & z0) == z0) [[likely]] {
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hz = sizeof(header);
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} else {
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@ -309,7 +338,9 @@ namespace xo {
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++(s.error_count_);
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s.last_error_ = AllocatorError(error::header_size_mask,
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s.error_count_,
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0 /*add_commit_z*/, s.committed_z_, reserved(s));
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0 /*add_commit_z*/,
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s.committed_z_,
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reserved(s));
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return nullptr;
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}
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}
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@ -318,32 +349,45 @@ namespace xo {
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assert(padding::is_aligned(z1));
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if (expand(s, allocated(s) + z1)) [[likely]] {
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if (store_header_flag) {
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(*(uint64_t *)s.free_) = header;
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if (remember_header_flag) {
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s.last_header_ = (uint64_t *)s.free_;
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}
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}
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byte * mem = s.free_ + hz;
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s.free_ += z1;
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log && log(xtag("self", s.config_.name_),
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xtag("hz", hz),
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xtag("z0", req_z),
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xtag("+pad", dz),
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xtag("z1", z1),
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xtag("size", size(s)),
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xtag("avail", available(s)));
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return mem;
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} else {
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/* error already captured */
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if (!expand(s, allocated(s) + z1)) [[unlikely]] {
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/* (error state already captured) */
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return nullptr;
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}
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if (store_header_flag) {
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/* capturing header */
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*(uint64_t *)s.free_ = header;
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if (retain_header_flag) {
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/* and rembering for subsequent
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* sub_alloc()
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*/
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s.last_header_ = (uint64_t *)s.free_;
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}
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}
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byte * mem = s.free_ + hz;
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s.free_ += z1;
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if (store_guard) {
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/* write guard bytes for overrun detection */
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::memset(s.free_,
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s.config_.guard_byte_,
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s.config_.guard_z_);
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s.free_ += s.config_.guard_z_;
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}
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log && log(xtag("self", s.config_.name_),
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xtag("hz", hz),
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xtag("z0", req_z),
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xtag("+pad", dz),
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xtag("z1", z1),
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xtag("size", size(s)),
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xtag("avail", available(s)));
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return mem;
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}
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void
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