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Merge pull request #34520 from vcaputo/mmap-cache-unused-min

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mmap-cache: enforce an unused windows minimum
This commit is contained in:
Yu Watanabe 2024-10-13 14:48:35 +09:00 committed by GitHub
commit 709fdcc75a
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2 changed files with 14 additions and 7 deletions
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13
src/libsystemd/sd-journal/mmap-cache.c
View File

@ -64,11 +64,13 @@ struct MMapCache {
LIST_HEAD(Window, unused);
Window *last_unused;
unsigned n_unused;
Window *windows_by_category[_MMAP_CACHE_CATEGORY_MAX];
};
#define WINDOWS_MIN 64
#define UNUSED_MIN 4
#if ENABLE_DEBUG_MMAP_CACHE
/* Tiny windows increase mmap activity and the chance of exposing unsafe use. */
@ -103,6 +105,7 @@ static Window* window_unlink(Window *w) {
if (m->last_unused == w)
m->last_unused = w->unused_prev;
LIST_REMOVE(unused, m->unused, w);
m->n_unused--;
}
for (unsigned i = 0; i < _MMAP_CACHE_CATEGORY_MAX; i++)
@ -160,7 +163,7 @@ static Window* window_add(MMapFileDescriptor *f, uint64_t offset, size_t size, v
MMapCache *m = mmap_cache_fd_cache(f);
Window *w;
if (!m->last_unused || m->n_windows <= WINDOWS_MIN) {
if (!m->last_unused || m->n_windows < WINDOWS_MIN || m->n_unused < UNUSED_MIN) {
/* Allocate a new window */
w = new(Window, 1);
if (!w)
@ -202,6 +205,7 @@ static void category_detach_window(MMapCache *m, MMapCacheCategory c) {
LIST_PREPEND(unused, m->unused, w);
if (!m->last_unused)
m->last_unused = w;
m->n_unused++;
w->flags |= WINDOW_IN_UNUSED;
#endif
}
@ -222,6 +226,7 @@ static void category_attach_window(MMapCache *m, MMapCacheCategory c, Window *w)
if (m->last_unused == w)
m->last_unused = w->unused_prev;
LIST_REMOVE(unused, m->unused, w);
m->n_unused--;
w->flags &= ~WINDOW_IN_UNUSED;
}
@ -239,7 +244,7 @@ static MMapCache* mmap_cache_free(MMapCache *m) {
assert(hashmap_isempty(m->fds));
hashmap_free(m->fds);
assert(!m->unused);
assert(!m->unused && m->n_unused == 0);
assert(m->n_windows == 0);
return mfree(m);
@ -430,8 +435,8 @@ found:
void mmap_cache_stats_log_debug(MMapCache *m) {
assert(m);
log_debug("mmap cache statistics: %u category cache hit, %u window list hit, %u miss",
m->n_category_cache_hit, m->n_window_list_hit, m->n_missed);
log_debug("mmap cache statistics: %u category cache hit, %u window list hit, %u miss, %u files, %u windows, %u unused",
m->n_category_cache_hit, m->n_window_list_hit, m->n_missed, hashmap_size(m->fds), m->n_windows, m->n_unused);
}
static void mmap_cache_process_sigbus(MMapCache *m) {

8
src/libsystemd/sd-journal/sd-journal.c
View File

@ -2542,6 +2542,10 @@ _public_ void sd_journal_close(sd_journal *j) {
sd_journal_flush_matches(j);
/* log stats before closing files so we can see the windows state */
if (j->mmap)
mmap_cache_stats_log_debug(j->mmap);
ordered_hashmap_free_with_destructor(j->files, journal_file_close);
iterated_cache_free(j->files_cache);
@ -2553,10 +2557,8 @@ _public_ void sd_journal_close(sd_journal *j) {
safe_close(j->inotify_fd);
if (j->mmap) {
mmap_cache_stats_log_debug(j->mmap);
if (j->mmap)
mmap_cache_unref(j->mmap);
}
hashmap_free_free(j->errors);