@samitouri / QOSAMI-WSL / commits / 88f76dd7

Address memory reclaim follow-ups from #41096 (#41171)

* Address follow-ups from PR #41096 - Parse the /proc/stat cpu line with std::regex instead of a manual strtoull cursor loop, while retaining the O_CLOEXEC bounded read. - Use drop_caches=3 in DropCache mode to also drop reclaimable slab (dentries/inodes), matching the SReclaimable slab counted by GetReclaimableCacheBytes. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0e37f3d5-68e7-4973-8c27-bf4329c8fd9b * Restrict /proc/stat field separators to spaces/tabs ECMAScript \s matches newlines, so on a truncated aggregate cpu line the optional irq/softirq/steal groups could consume digits from the next line in the read buffer. Use [ \t] so the match cannot span lines. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0e37f3d5-68e7-4973-8c27-bf4329c8fd9b --------- Co-authored-by: Ben Hillis <benhill@ntdev.microsoft.com> Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0e37f3d5-68e7-4973-8c27-bf4329c8fd9b

Ben Hillis committed Jul 27, 2026 at 12:26 UTC 88f76dd7dc2412af452834d753a0c6ce4af2a3ac

1 file changed +17 -28

src/linux/init/util.cpp

+17 -28

@@ -3633,46 +3633,30 @@ Return Value:

3633 buffer[result] = '\0';

3634

3635 //

3636 - // Format: "cpu user nice system idle iowait irq softirq steal ...". Fields after steal are ignored.

3636 + // Format: "cpu user nice system idle iowait irq softirq steal ...". The user, nice, system, idle,

3637 + // and iowait fields are required; irq, softirq, and steal are optional and any fields after steal

3638 + // are ignored.

3639 //

3640

3639 - if (strncmp(buffer, "cpu ", 4) != 0)

3641 + static const std::regex cpuLine{R"(^cpu[ \t]+(\d+)[ \t]+(\d+)[ \t]+(\d+)[ \t]+(\d+)[ \t]+(\d+)(?:[ \t]+(\d+))?(?:[ \t]+(\d+))?(?:[ \t]+(\d+))?)"};

3642 + std::cmatch match;

3643 + if (!std::regex_search(buffer, match, cpuLine))

3644 {

3641 - LOG_ERROR("/proc/stat first line missing cpu label");

3645 + LOG_ERROR("failed to parse /proc/stat cpu line");

3646 return false;

3647 }

3648

3649 unsigned long long fields[8] = {};

3646 - const char* cursor = buffer + 3;

3647 - int parsed = 0;

3648 - for (; parsed < static_cast<int>(COUNT_OF(fields)); parsed += 1)

3650 + for (size_t index = 0; index < COUNT_OF(fields); index += 1)

3651 {

3650 - char* end = nullptr;

3651 - const unsigned long long value = strtoull(cursor, &end, 10);

3652 - if (end == cursor)

3652 + if (match[index + 1].matched)

3653 {

3654 - break;

3654 + fields[index] = strtoull(match[index + 1].first, nullptr, 10);

3655 }

3656 -

3657 - fields[parsed] = value;

3658 - cursor = end;

3659 - }

3660 -

3661 - if (parsed < 5)

3662 - {

3663 - LOG_ERROR("failed to parse /proc/stat cpu line (parsed {})", parsed);

3664 - return false;

3656 }

3657

3658 Idle = fields[3] + fields[4];

3668 - Busy = 0;

3669 - for (int index = 0; index < parsed; index += 1)

3670 - {

3671 - if (index != 3 && index != 4)

3672 - {

3673 - Busy += fields[index];

3674 - }

3675 - }

3659 + Busy = fields[0] + fields[1] + fields[2] + fields[5] + fields[6] + fields[7];

3660

3661 return true;

3662 }

@@ -3957,7 +3941,12 @@ try

3941 }

3942 else if (!droppedThisIdlePeriod)

3943 {

3960 - if (WriteToFile("/proc/sys/vm/drop_caches", "1\n") == 0)

3944 + //

3945 + // drop_caches=3 frees the page cache along with reclaimable slab (dentries and

3946 + // inodes), matching the SReclaimable slab counted by GetReclaimableCacheBytes.

3947 + //

3948 +

3949 + if (WriteToFile("/proc/sys/vm/drop_caches", "3\n") == 0)

3950 {

3951 droppedThisIdlePeriod = true;

3952 reclaimed = true;