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Date:   Tue, 14 Jan 2020 17:18:57 +0100
From:   David Sterba <dsterba@suse.cz>
To:     Mikhail Zaslonko <zaslonko@linux.ibm.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Chris Mason <clm@fb.com>, Josef Bacik <josef@toxicpanda.com>,
        David Sterba <dsterba@suse.com>,
        Richard Purdie <rpurdie@rpsys.net>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Eduard Shishkin <edward6@linux.ibm.com>,
        Ilya Leoshkevich <iii@linux.ibm.com>,
        linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4] btrfs: Use larger zlib buffer for s390 hardware
 compression
Message-ID: <20200114161857.GD3929@suse.cz>
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        Mikhail Zaslonko <zaslonko@linux.ibm.com>,
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        Josef Bacik <josef@toxicpanda.com>, David Sterba <dsterba@suse.com>,
        Richard Purdie <rpurdie@rpsys.net>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
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        linux-kernel@vger.kernel.org
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 <20200108105103.29028-1-zaslonko@linux.ibm.com>
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On Wed, Jan 08, 2020 at 11:51:03AM +0100, Mikhail Zaslonko wrote:
> In order to benefit from s390 zlib hardware compression support,
> increase the btrfs zlib workspace buffer size from 1 to 4 pages (if
> s390 zlib hardware support is enabled on the machine). This brings up
> to 60% better performance in hardware on s390 compared to the PAGE_SIZE
> buffer and much more compared to the software zlib processing in btrfs.
> In case of memory pressure, fall back to a single page buffer during
> workspace allocation.
> The data compressed with larger input buffers will still conform to zlib
> standard and thus can be decompressed also on a systems that uses only
> PAGE_SIZE buffer for btrfs zlib.
> 
> Signed-off-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>

Reviewed-by: David Sterba <dsterba@suse.com>