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Thu, 31 Jan 2019 16:51:56 GMT Received: from ca-dmjordan1.us.oracle.com (/10.211.9.48) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 31 Jan 2019 08:51:56 -0800 Date: Thu, 31 Jan 2019 11:52:15 -0500 From: Daniel Jordan To: Kirill Tkhai Cc: akpm@linux-foundation.org, mhocko@suse.com, hannes@cmpxchg.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: Do not allocate duplicate stack variables in shrink_page_list() Message-ID: <20190131165215.i3iotkg64iz5ithp@ca-dmjordan1.us.oracle.com> References: <154894900030.5211.12104993874109647641.stgit@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <154894900030.5211.12104993874109647641.stgit@localhost.localdomain> User-Agent: NeoMutt/20180323-268-5a959c X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9152 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1901310129 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jan 31, 2019 at 06:37:02PM +0300, Kirill Tkhai wrote: > On path shrink_inactive_list() ---> shrink_page_list() > we allocate stack variables for the statistics twice. > This is completely useless, and this just consumes stack > much more, then we really need. > > The patch kills duplicate stack variables from shrink_page_list(), > and this reduce stack usage and object file size significantly: > > Stack usage: > Before: vmscan.c:1122:22:shrink_page_list 648 static > After: vmscan.c:1122:22:shrink_page_list 616 static > > Size of vmscan.o: > text data bss dec hex filename > Before: 56866 4720 128 61714 f112 mm/vmscan.o > After: 56770 4720 128 61618 f0b2 mm/vmscan.o > > Signed-off-by: Kirill Tkhai > --- > mm/vmscan.c | 44 ++++++++++++++------------------------------ > 1 file changed, 14 insertions(+), 30 deletions(-) > @@ -1534,6 +1517,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone, > .priority = DEF_PRIORITY, > .may_unmap = 1, > }; > + struct reclaim_stat dummy_stat; > unsigned long ret; > struct page *page, *next; > LIST_HEAD(clean_pages); > @@ -1547,7 +1531,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone, > } > > ret = shrink_page_list(&clean_pages, zone->zone_pgdat, &sc, > - TTU_IGNORE_ACCESS, NULL, true); > + TTU_IGNORE_ACCESS, &dummy_stat, true); > list_splice(&clean_pages, page_list); > mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, -ret); > return ret; Stack usage stays the same coming from reclaim_clean_pages_from_list, with a dummy variable added back after many were taken away in 3c710c1ad11b ("mm, vmscan: extract shrink_page_list..."). But overall seems like a win to me. You can add Reviewed-by: Daniel Jordan