Messages in this thread Patch in this message | | | From | Davidlohr Bueso <> | Subject | [PATCH 2/2] ipc/sem: play nicer with large nsops allocations | Date | Thu, 3 Aug 2017 11:41:36 -0700 |
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Replacing semop()'s kmalloc for kvmalloc was originally proposed by Manfred on the premise that it can be called for large (than order-1) sizes. For example, while Oracle recommends setting SEMOPM to a _minimum_ of 100, some distros[1] encourage the setting to be a factor of the amount of db tasks (PROCESSES), which can get fishy for large systems (easily going beyond 1000).
[1] An Example of Semaphore Settings https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/5/html/Tuning_and_Optimizing_Red_Hat_Enterprise_Linux_for_Oracle_9i_and_10g_Databases/sect-Oracle_9i_and_10g_Tuning_Guide-Setting_Semaphores-An_Example_of_Semaphore_Settings.html
So lets just convert this to kvmalloc, just like the rest of the allocations we do in ipc. While the fallback vmalloc obviously involves more overhead, this by far the uncommon path, and it's better for the user than just erroring out with kmalloc.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de> --- ipc/sem.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/ipc/sem.c b/ipc/sem.c index e9980cba07fd..30d80bfc1ec8 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -1784,7 +1784,7 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, if (nsops > ns->sc_semopm) return -E2BIG; if (nsops > SEMOPM_FAST) { - sops = kmalloc(sizeof(*sops)*nsops, GFP_KERNEL); + sops = kvmalloc(sizeof(*sops)*nsops, GFP_KERNEL); if (sops == NULL) return -ENOMEM; } @@ -2016,7 +2016,7 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, rcu_read_unlock(); out_free: if (sops != fast_sops) - kfree(sops); + kvfree(sops); return error; } -- 2.12.0
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