diff options
| author | Uros Bizjak <ubizjak@gmail.com> | 2023-09-04 17:08:49 +0200 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-10-04 10:32:20 -0700 |
| commit | 77cd814835df22e177a9caac1b046f7ffdfeedd0 (patch) | |
| tree | 0c93012406c3a1f6c74a4de1822524dcfa90f527 /mm/vmstat.c | |
| parent | 91e79d22be75fec88ae58d274a7c9e49d6215099 (diff) | |
mm/vmstat: use this_cpu_try_cmpxchg in mod_{zone,node}_state
Use this_cpu_try_cmpxchg instead of this_cpu_cmpxchg (*ptr, old, new) ==
old in mod_zone_state and mod_node_state. x86 CMPXCHG instruction returns
success in ZF flag, so this change saves a compare after cmpxchg (and
related move instruction in front of cmpxchg).
Also, try_cmpxchg implicitly assigns old *ptr value to "old" when cmpxchg
fails. There is no need to re-read the value in the loop.
No functional change intended.
Link: https://lkml.kernel.org/r/20230904150917.8318-1-ubizjak@gmail.com
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/vmstat.c')
| -rw-r--r-- | mm/vmstat.c | 18 |
1 files changed, 10 insertions, 8 deletions
diff --git a/mm/vmstat.c b/mm/vmstat.c index 00e81e99c6ee..894e4c88d241 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -559,8 +559,10 @@ static inline void mod_zone_state(struct zone *zone, { struct per_cpu_zonestat __percpu *pcp = zone->per_cpu_zonestats; s8 __percpu *p = pcp->vm_stat_diff + item; - long o, n, t, z; + long n, t, z; + s8 o; + o = this_cpu_read(*p); do { z = 0; /* overflow to zone counters */ @@ -576,8 +578,7 @@ static inline void mod_zone_state(struct zone *zone, */ t = this_cpu_read(pcp->stat_threshold); - o = this_cpu_read(*p); - n = delta + o; + n = delta + (long)o; if (abs(n) > t) { int os = overstep_mode * (t >> 1) ; @@ -586,7 +587,7 @@ static inline void mod_zone_state(struct zone *zone, z = n + os; n = -os; } - } while (this_cpu_cmpxchg(*p, o, n) != o); + } while (!this_cpu_try_cmpxchg(*p, &o, n)); if (z) zone_page_state_add(z, zone, item); @@ -616,7 +617,8 @@ static inline void mod_node_state(struct pglist_data *pgdat, { struct per_cpu_nodestat __percpu *pcp = pgdat->per_cpu_nodestats; s8 __percpu *p = pcp->vm_node_stat_diff + item; - long o, n, t, z; + long n, t, z; + s8 o; if (vmstat_item_in_bytes(item)) { /* @@ -629,6 +631,7 @@ static inline void mod_node_state(struct pglist_data *pgdat, delta >>= PAGE_SHIFT; } + o = this_cpu_read(*p); do { z = 0; /* overflow to node counters */ @@ -644,8 +647,7 @@ static inline void mod_node_state(struct pglist_data *pgdat, */ t = this_cpu_read(pcp->stat_threshold); - o = this_cpu_read(*p); - n = delta + o; + n = delta + (long)o; if (abs(n) > t) { int os = overstep_mode * (t >> 1) ; @@ -654,7 +656,7 @@ static inline void mod_node_state(struct pglist_data *pgdat, z = n + os; n = -os; } - } while (this_cpu_cmpxchg(*p, o, n) != o); + } while (!this_cpu_try_cmpxchg(*p, &o, n)); if (z) node_page_state_add(z, pgdat, item); |