et>, Chris Zankel <ch...@zankel.net>, Michal Simek <mon...@monstr.eu>, Thomas
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Filippov <jcmvb...@gmail.com>, linux-ker...@vger.kernel.org, Dinh Nguyen
<dingu...@kernel.org>, Palmer Dabbelt <pal...@dabbelt.com>, Sven Schnelle
<sv...@linux.ibm.com>, Guo Ren <guo...@kernel.org>, Borislav Petkov
<b...@alien8.de>, Johannes Berg <johan...@sipsolutions.net>,
linuxppc-dev@lists.ozlabs.org, "David S . Miller" <da...@davemloft.net>
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* Peter Xu <pet...@redhat.com> wrote:
> This patch provides a ~12% perf boost on my aarch64 test VM with a simple
> program sequentially dirtying 400MB shmem file being mmap()ed and these are
> the time it needs:
>
> Before: 650.980 ms (+-1.94%)
> After: 569.396 ms (+-1.38%)
Nice!
> arch/x86/mm/fault.c | 4 ++++
Reviewed-by: Ingo Molnar <mi...@kernel.org>
Minor comment typo:
> + /*
> + * We should do the same as VM_FAULT_RETRY, but let's not
> + * return -EBUSY since that's not reflecting the reality on
> + * what has happened - we've just fully completed a page
> + * fault, with the mmap lock released. Use -EAGAIN to show
> + * that we want to take the mmap lock _again_.
> + */
s/reflecting the reality on what has happened
/reflecting the reality of what has happened
> ret = handle_mm_fault(vma, address, fault_flags, NULL);
> +
> + if (ret & VM_FAULT_COMPLETED) {
> + /*
> + * NOTE: it's a pity that we need to retake the lock here
> + * to pair with the unlock() in the callers. Ideally we
> + * could tell the callers so they do not need to unlock.
> + */
> + mmap_read_lock(mm);
> + *unlocked = true;
> + return 0;
Indeed that's a pity - I guess more performance could be gained here,
especially in highly parallel threaded workloads?
Thanks,
Ingo
