From: Olivier Houchard <ohouchard@haproxy.com>
Date: Tue, 20 Oct 2026 13:25:19 +0000 (+0200)
Subject: OPTIM: fd: make each thread group's polled_mask NUMA-local
X-Git-Tag: v3.5-dev10~92
X-Git-Url: https://git.kaiwu.me/?a=commitdiff_plain;h=840d0ea42845a91a8c4ca7b4ac7f649bc928038f;p=haproxy.git

OPTIM: fd: make each thread group's polled_mask NUMA-local

The polled_mask array was left aside the fdtab's NUMA placement:
its slices are not padded to the page size, so a page can be shared
between two groups, and calloc() zeroes it eagerly on the boot
thread when the allocation is served from the heap. Allocate it
with mmap() and pad the slices as the fdtab: nothing is copied
nor zeroed, the pages are born zeroed and each group's masks are
written by its own threads, bound before they first touch them, so
the lazy faulting places them on the right node by itself.
---

diff --git a/src/fd.c b/src/fd.c
index 5544d2105..3591d912b 100644
--- a/src/fd.c
+++ b/src/fd.c
@@ -105,6 +105,7 @@ static struct fdtab *_fdtab;
 static size_t fdtab_alloc_size;  /* size of the mmap() area backing _fdtab, for munmap() */
 THREAD_LOCAL struct polled_mask *polled_mask = NULL;  /* Array for the polled_mask of each fd */
 static struct polled_mask *_polled_mask;
+static size_t polled_mask_alloc_size;  /* size of the mmap() area backing _polled_mask, for munmap() */
 int totalconn;                  /* total # of terminated sessions */
 int actconn;                    /* # of active sessions */
 
@@ -1219,6 +1220,7 @@ static void free_pollers_per_thread()
 int init_pollers()
 {
 	size_t fdtab_stride;
+	size_t pm_stride;
 	int p;
 	struct poller *bp;
 	int nbfdtab;
@@ -1267,7 +1269,16 @@ int init_pollers()
 	thread_bind_to_cpu_map(0, 0);
 	vma_set_name(_fdtab, fdtab_alloc_size, "fd", "fdtab");
 
-	if ((_polled_mask = calloc(global.maxsock, nbfdtab * sizeof(*polled_mask))) == NULL) {
+	/* as the fdtab, allocate the polled_mask with mmap() and slice it
+	 * at the page size, so that each page is only accessed by the
+	 * thread group that owns it.
+	 */
+	pm_stride = (array_size_or_fail(global.maxsock, sizeof(*polled_mask)) + page_size - 1) & ~(page_size - 1);
+	polled_mask_alloc_size = array_size_or_fail(nbfdtab, pm_stride);
+	_polled_mask = mmap(NULL, polled_mask_alloc_size, PROT_READ | PROT_WRITE,
+	                    MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	if (_polled_mask == MAP_FAILED) {
+		_polled_mask = NULL;
 		ha_alert("Not enough memory to allocate %d entries for polled_mask!\n", global.maxsock);
 		goto fail_polledmask;
 	}
@@ -1277,13 +1288,13 @@ int init_pollers()
 	 */
 	for (p = 0; p < global.nbtgroups; p++) {
 		if (global.tune.options & GTUNE_NO_TG_FD_SHARING)
-			ha_tgroup_ctx[p].polled_mask = _polled_mask + p * global.maxsock;
+			ha_tgroup_ctx[p].polled_mask = (struct polled_mask *)((char *)_polled_mask + p * pm_stride);
 		else
 			ha_tgroup_ctx[p].polled_mask = _polled_mask;
 	}
 	/* immediately set it for the boot thread as well */
 	polled_mask = ha_tgroup_ctx[0].polled_mask;
-	vma_set_name(_polled_mask, global.maxsock * sizeof(*polled_mask) * nbfdtab, "fd", "polled_mask");
+	vma_set_name(_polled_mask, polled_mask_alloc_size, "fd", "polled_mask");
 
 	for (p = 0; p < MAX_TGROUPS; p++)
 		update_list[p].first = update_list[p].last = -1;
@@ -1317,7 +1328,7 @@ redo:
 	} while (!bp || bp->pref == 0);
 
  fail_info:
-	free(_polled_mask);
+	munmap(_polled_mask, polled_mask_alloc_size);
 	_polled_mask = polled_mask = NULL;
  fail_polledmask:
 	munmap(_fdtab, fdtab_alloc_size);
@@ -1346,8 +1357,8 @@ void deinit_pollers() {
 	 */
 	munmap(_fdtab, fdtab_alloc_size);
 	_fdtab = fdtab = NULL;
-	ha_free(&_polled_mask);
-	polled_mask = NULL;
+	munmap(_polled_mask, polled_mask_alloc_size);
+	_polled_mask = polled_mask = NULL;
 }
 
 /*