From: Andi Kleen <ak@linux.intel.com>
To: Timofey Titovets <nefelim4ag@gmail.com>
Cc: linux-mm@kvack.org
Subject: Re: [PATCH] KSM: Replace jhash2 with xxhash
Date: Thu, 21 Sep 2017 08:36:57 -0700 [thread overview]
Message-ID: <8760ccdpwm.fsf@linux.intel.com> (raw)
In-Reply-To: <20170921074519.9333-1-nefelim4ag@gmail.com> (Timofey Titovets's message of "Thu, 21 Sep 2017 10:45:19 +0300")
Timofey Titovets <nefelim4ag@gmail.com> writes:
> xxhash much faster then jhash,
> ex. for x86_64 host:
> PAGE_SIZE: 4096, loop count: 1048576
> jhash2: 0xacbc7a5b time: 1907 ms, th: 2251.9 MiB/s
> xxhash32: 0x570da981 time: 739 ms, th: 5809.4 MiB/s
> xxhash64: 0xa1fa032ab85bbb62 time: 371 ms, th: 11556.6 MiB/s
>
> xxhash64 on x86_32 work with ~ same speed as jhash2.
> xxhash32 on x86_32 work with ~ same speed as for x86_64
Which CPU is that?
>
> So replace jhash with xxhash,
> and use fastest version for current target ARCH.
Can you do some macro-benchmarking too? Something that uses
KSM and show how the performance changes.
You could manually increase the scan rate to make it easier
to see.
> @@ -51,6 +52,12 @@
> #define DO_NUMA(x) do { } while (0)
> #endif
>
> +#if BITS_PER_LONG == 64
> +typedef u64 xxhash;
> +#else
> +typedef u32 xxhash;
> +#endif
This should be in xxhash.h ?
xxhash_t would seem to be a better name.
> - u32 checksum;
> + xxhash checksum;
> void *addr = kmap_atomic(page);
> - checksum = jhash2(addr, PAGE_SIZE / 4, 17);
> +#if BITS_PER_LONG == 64
> + checksum = xxh64(addr, PAGE_SIZE, 0);
> +#else
> + checksum = xxh32(addr, PAGE_SIZE, 0);
> +#endif
This should also be generic in xxhash.h
-Andi
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next prev parent reply other threads:[~2017-09-21 15:36 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-21 7:45 [PATCH] KSM: Replace jhash2 with xxhash Timofey Titovets
2017-09-21 15:36 ` Andi Kleen [this message]
2017-09-21 17:35 ` Timofey Titovets
2017-09-21 20:05 ` Andi Kleen
2017-09-21 21:37 ` Timofey Titovets
2017-09-21 22:06 ` Andi Kleen
2017-09-22 8:44 ` Christian Borntraeger
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