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Fri, 2 Aug 2019 11:08:41 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 93BA7AF33; Fri, 2 Aug 2019 15:08:39 +0000 (UTC) Subject: Re: [PATCH 03/24] mm: factor shrinker work calculations To: Dave Chinner , linux-xfs@vger.kernel.org Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org References: <20190801021752.4986-1-david@fromorbit.com> <20190801021752.4986-4-david@fromorbit.com> From: Nikolay Borisov Openpgp: preference=signencrypt Autocrypt: addr=nborisov@suse.com; prefer-encrypt=mutual; keydata= mQINBFiKBz4BEADNHZmqwhuN6EAzXj9SpPpH/nSSP8YgfwoOqwrP+JR4pIqRK0AWWeWCSwmZ T7g+RbfPFlmQp+EwFWOtABXlKC54zgSf+uulGwx5JAUFVUIRBmnHOYi/lUiE0yhpnb1KCA7f u/W+DkwGerXqhhe9TvQoGwgCKNfzFPZoM+gZrm+kWv03QLUCr210n4cwaCPJ0Nr9Z3c582xc bCUVbsjt7BN0CFa2BByulrx5xD9sDAYIqfLCcZetAqsTRGxM7LD0kh5WlKzOeAXj5r8DOrU2 GdZS33uKZI/kZJZVytSmZpswDsKhnGzRN1BANGP8sC+WD4eRXajOmNh2HL4P+meO1TlM3GLl EQd2shHFY0qjEo7wxKZI1RyZZ5AgJnSmehrPCyuIyVY210CbMaIKHUIsTqRgY5GaNME24w7h TyyVCy2qAM8fLJ4Vw5bycM/u5xfWm7gyTb9V1TkZ3o1MTrEsrcqFiRrBY94Rs0oQkZvunqia c+NprYSaOG1Cta14o94eMH271Kka/reEwSZkC7T+o9hZ4zi2CcLcY0DXj0qdId7vUKSJjEep c++s8ncFekh1MPhkOgNj8pk17OAESanmDwksmzh1j12lgA5lTFPrJeRNu6/isC2zyZhTwMWs k3LkcTa8ZXxh0RfWAqgx/ogKPk4ZxOXQEZetkEyTFghbRH2BIwARAQABtCNOaWtvbGF5IEJv cmlzb3YgPG5ib3Jpc292QHN1c2UuY29tPokCOAQTAQIAIgUCWIo48QIbAwYLCQgHAwIGFQgC CQoLBBYCAwECHgECF4AACgkQcb6CRuU/KFc0eg/9GLD3wTQz9iZHMFbjiqTCitD7B6dTLV1C ddZVlC8Hm/TophPts1bWZORAmYIihHHI1EIF19+bfIr46pvfTu0yFrJDLOADMDH+Ufzsfy2v HSqqWV/nOSWGXzh8bgg/ncLwrIdEwBQBN9SDS6aqsglagvwFD91UCg/TshLlRxD5BOnuzfzI Leyx2c6YmH7Oa1R4MX9Jo79SaKwdHt2yRN3SochVtxCyafDlZsE/efp21pMiaK1HoCOZTBp5 VzrIP85GATh18pN7YR9CuPxxN0V6IzT7IlhS4Jgj0NXh6vi1DlmKspr+FOevu4RVXqqcNTSS E2rycB2v6cttH21UUdu/0FtMBKh+rv8+yD49FxMYnTi1jwVzr208vDdRU2v7Ij/TxYt/v4O8 V+jNRKy5Fevca/1xroQBICXsNoFLr10X5IjmhAhqIH8Atpz/89ItS3+HWuE4BHB6RRLM0gy8 T7rN6ja+KegOGikp/VTwBlszhvfLhyoyjXI44Tf3oLSFM+8+qG3B7MNBHOt60CQlMkq0fGXd mm4xENl/SSeHsiomdveeq7cNGpHi6i6ntZK33XJLwvyf00PD7tip/GUj0Dic/ZUsoPSTF/mG EpuQiUZs8X2xjK/AS/l3wa4Kz2tlcOKSKpIpna7V1+CMNkNzaCOlbv7QwprAerKYywPCoOSC 7P25Ag0EWIoHPgEQAMiUqvRBZNvPvki34O/dcTodvLSyOmK/MMBDrzN8Cnk302XfnGlW/YAQ csMWISKKSpStc6tmD+2Y0z9WjyRqFr3EGfH1RXSv9Z1vmfPzU42jsdZn667UxrRcVQXUgoKg QYx055Q2FdUeaZSaivoIBD9WtJq/66UPXRRr4H/+Y5FaUZx+gWNGmBT6a0S/GQnHb9g3nonD jmDKGw+YO4P6aEMxyy3k9PstaoiyBXnzQASzdOi39BgWQuZfIQjN0aW+Dm8kOAfT5i/yk59h VV6v3NLHBjHVw9kHli3jwvsizIX9X2W8tb1SefaVxqvqO1132AO8V9CbE1DcVT8fzICvGi42 FoV/k0QOGwq+LmLf0t04Q0csEl+h69ZcqeBSQcIMm/Ir+NorfCr6HjrB6lW7giBkQl6hhomn l1mtDP6MTdbyYzEiBFcwQD4terc7S/8ELRRybWQHQp7sxQM/Lnuhs77MgY/e6c5AVWnMKd/z MKm4ru7A8+8gdHeydrRQSWDaVbfy3Hup0Ia76J9FaolnjB8YLUOJPdhI2vbvNCQ2ipxw3Y3c KhVIpGYqwdvFIiz0Fej7wnJICIrpJs/+XLQHyqcmERn3s/iWwBpeogrx2Lf8AGezqnv9woq7 OSoWlwXDJiUdaqPEB/HmGfqoRRN20jx+OOvuaBMPAPb+aKJyle8zABEBAAGJAh8EGAECAAkF AliKBz4CGwwACgkQcb6CRuU/KFdacg/+M3V3Ti9JYZEiIyVhqs+yHb6NMI1R0kkAmzsGQ1jU zSQUz9AVMR6T7v2fIETTT/f5Oout0+Hi9cY8uLpk8CWno9V9eR/B7Ifs2pAA8lh2nW43FFwp IDiSuDbH6oTLmiGCB206IvSuaQCp1fed8U6yuqGFcnf0ZpJm/sILG2ECdFK9RYnMIaeqlNQm iZicBY2lmlYFBEaMXHoy+K7nbOuizPWdUKoKHq+tmZ3iA+qL5s6Qlm4trH28/fPpFuOmgP8P K+7LpYLNSl1oQUr+WlqilPAuLcCo5Vdl7M7VFLMq4xxY/dY99aZx0ZJQYFx0w/6UkbDdFLzN upT7NIN68lZRucImffiWyN7CjH23X3Tni8bS9ubo7OON68NbPz1YIaYaHmnVQCjDyDXkQoKC R82Vf9mf5slj0Vlpf+/Wpsv/TH8X32ajva37oEQTkWNMsDxyw3aPSps6MaMafcN7k60y2Wk/ TCiLsRHFfMHFY6/lq/c0ZdOsGjgpIK0G0z6et9YU6MaPuKwNY4kBdjPNBwHreucrQVUdqRRm RcxmGC6ohvpqVGfhT48ZPZKZEWM+tZky0mO7bhZYxMXyVjBn4EoNTsXy1et9Y1dU3HVJ8fod 5UqrNrzIQFbdeM0/JqSLrtlTcXKJ7cYFa9ZM2AP7UIN9n1UWxq+OPY9YMOewVfYtL8M= Message-ID: Date: Fri, 2 Aug 2019 18:08:37 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190801021752.4986-4-david@fromorbit.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 1.08.19 г. 5:17 ч., Dave Chinner wrote: > From: Dave Chinner > > Start to clean up the shrinker code by factoring out the calculation > that determines how much work to do. This separates the calculation > from clamping and other adjustments that are done before the > shrinker work is run. > > Also convert the calculation for the amount of work to be done to > use 64 bit logic so we don't have to keep jumping through hoops to > keep calculations within 32 bits on 32 bit systems. > > Signed-off-by: Dave Chinner > --- > mm/vmscan.c | 74 ++++++++++++++++++++++++++++++++++------------------- > 1 file changed, 47 insertions(+), 27 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index ae3035fe94bc..b7472953b0e6 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -464,13 +464,45 @@ EXPORT_SYMBOL(unregister_shrinker); > > #define SHRINK_BATCH 128 > > +/* > + * Calculate the number of new objects to scan this time around. Return > + * the work to be done. If there are freeable objects, return that number in > + * @freeable_objects. > + */ > +static int64_t shrink_scan_count(struct shrink_control *shrinkctl, > + struct shrinker *shrinker, int priority, > + int64_t *freeable_objects) nit: make the return parm definition also uin64_t, also we have u64 types. > +{ > + uint64_t delta; > + uint64_t freeable; > + > + freeable = shrinker->count_objects(shrinker, shrinkctl); > + if (freeable == 0 || freeable == SHRINK_EMPTY) > + return freeable; > + > + if (shrinker->seeks) { > + delta = freeable >> (priority - 2); > + do_div(delta, shrinker->seeks); a comment about the reasoning behind this calculation would be nice. > + } else { > + /* > + * These objects don't require any IO to create. Trim > + * them aggressively under memory pressure to keep > + * them from causing refetches in the IO caches. > + */ > + delta = freeable / 2; > + } > + > + *freeable_objects = freeable; > + return delta > 0 ? delta : 0; > +} > + > static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, > struct shrinker *shrinker, int priority) > { > unsigned long freed = 0; > - unsigned long long delta; > long total_scan; > - long freeable; > + int64_t freeable_objects = 0; > + int64_t scan_count; why int and not uint64 ? We can never have negative object count, right? > long nr; > long new_nr; > int nid = shrinkctl->nid; > @@ -481,9 +513,10 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, > if (!(shrinker->flags & SHRINKER_NUMA_AWARE)) > nid = 0; > > - freeable = shrinker->count_objects(shrinker, shrinkctl); > - if (freeable == 0 || freeable == SHRINK_EMPTY) > - return freeable; > + scan_count = shrink_scan_count(shrinkctl, shrinker, priority, > + &freeable_objects); > + if (scan_count == 0 || scan_count == SHRINK_EMPTY) > + return scan_count; > > /* > * copy the current shrinker scan count into a local variable > @@ -492,25 +525,11 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, > */ > nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0); > > - total_scan = nr; > - if (shrinker->seeks) { > - delta = freeable >> priority; > - delta *= 4; > - do_div(delta, shrinker->seeks); > - } else { > - /* > - * These objects don't require any IO to create. Trim > - * them aggressively under memory pressure to keep > - * them from causing refetches in the IO caches. > - */ > - delta = freeable / 2; > - } > - > - total_scan += delta; > + total_scan = nr + scan_count; > if (total_scan < 0) { > pr_err("shrink_slab: %pS negative objects to delete nr=%ld\n", > shrinker->scan_objects, total_scan); > - total_scan = freeable; > + total_scan = scan_count; > next_deferred = nr; > } else > next_deferred = total_scan; > @@ -527,19 +546,20 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, > * Hence only allow the shrinker to scan the entire cache when > * a large delta change is calculated directly. > */ > - if (delta < freeable / 4) > - total_scan = min(total_scan, freeable / 2); > + if (scan_count < freeable_objects / 4) > + total_scan = min_t(long, total_scan, freeable_objects / 2); > > /* > * Avoid risking looping forever due to too large nr value: > * never try to free more than twice the estimate number of > * freeable entries. > */ > - if (total_scan > freeable * 2) > - total_scan = freeable * 2; > + if (total_scan > freeable_objects * 2) > + total_scan = freeable_objects * 2; > > trace_mm_shrink_slab_start(shrinker, shrinkctl, nr, > - freeable, delta, total_scan, priority); > + freeable_objects, scan_count, > + total_scan, priority); > > /* > * If the shrinker can't run (e.g. due to gfp_mask constraints), then > @@ -564,7 +584,7 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, > * possible. > */ > while (total_scan >= batch_size || > - total_scan >= freeable) { > + total_scan >= freeable_objects) { > unsigned long ret; > unsigned long nr_to_scan = min(batch_size, total_scan); > >