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X-IronPort-AV: E=McAfee;i="6500,9779,10603"; a="391829564" X-IronPort-AV: E=Sophos;i="5.97,253,1669104000"; d="scan'208";a="391829564" Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Jan 2023 00:33:47 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10603"; a="787460332" X-IronPort-AV: E=Sophos;i="5.97,253,1669104000"; d="scan'208";a="787460332" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Jan 2023 00:33:45 -0800 From: "Huang, Ying" To: Longlong Xia Cc: , , , , , Subject: Re: [RFC PATCH] mm/swapfile: add cond_resched() in get_swap_pages() References: <20230128072014.1030445-1-xialonglong1@huawei.com> Date: Sat, 28 Jan 2023 16:29:02 +0800 In-Reply-To: <20230128072014.1030445-1-xialonglong1@huawei.com> (Longlong Xia's message of "Sat, 28 Jan 2023 07:20:14 +0000") Message-ID: <87ilgrcbap.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 22CCF40007 X-Stat-Signature: tppwnpqbtj78k9sna8gcxuxnggg8kwy4 X-Rspam-User: X-HE-Tag: 1674894829-302130 X-HE-Meta: U2FsdGVkX18gBnyNgT4nzRItC+K1VJq3Oy0i5LTYNviNj9Vnao5NFHFOcc9o6OSGhzURRORUSK9GfjZMLE3B1Yw+YT+pfFaJ/sOWUqbRFcjxvIQfUs4LouDZD7G+04ZyJ+JDSXeWFAZw1QxndbP+1K765fzxoIjV9AdThH7tLoMzp9e/kEhAiZ7yCu55h0r1AKw0URSGgvCopEcX54ZztUyElRFzQ3nDGEjimTtBsobFN19I+JFxiQTTpvIhHvWLj49fGqZ9rP1Hp261IUZE1kpnLWtFD5zMPcIvzMmZ4+NjZuBnS8D8CDpN9Vv7g1qNQT1r0zwZJwgpQRg654OKa9TyrVbqYcfmAW4hVBGqdYJcyfceEuzex3/94btnExV/tKKU+Q0x/VChPK8WL1MXjyqffHtMzgKr68Bp+nCljjPHKg2uSK/1GT6V7dIhDRPfi2JE0weGOUWWMbWOR05ehjDvNBrFj4l8dlUBs1wgcWNXKaJuFcbJa9kMo1QYwvqN4vCd0j9aqEJxxqIYpSgRNLXfgCYgxj2fjTj3mmgpdo6c/Cx0Kpb+MfXyIuSvcYkRIn7xPb2yUlf+8lF6JR1gSY0c+uCKNZ1IIuPhw4ngzLAJrpTMaPAPtH5ChrVst/4fXF65yf7Blffq7fXBnFMiuYY0IhQlvpHSMN/T5kyYAm4t49VX8y/QB6Ito+Zkq3TiBM01P9o7FuH/7ULafdg6wO9W5G+lpYcxzoHzgIS2Fwi5TWaUCAxej5uGDrff8Ba7A7Tdup49Y/+g+10Fjc+quSqQpuJ2rcS2LPGbQ3wvrfXoJ/akoxNVuphgPtM01MkABnTgSNYTXQsx++v6i0CS54MPzn51fAwhG7EafN0Ff+/SrdkgSFunlN7dSketz/yCpbIHCedFokC96bO6tO7xTU6RKWSuda4U7zHgoDyuWxEXfS8HDVgEeQ4LUii4E+G9fZNeZhLscIb8/gphoq+ I2viRx0I xP3rkc5QlMa1zvFXS5vA7/DbvkCcPgGWueZnW+zHpMT/EMT2eT2bBmMioYfDupEZGwCn694NytRNpV/hF6W/8J2tHYI/EAy0suB+z6w5qATB+NmtiU0HoOKVhM2bb+6gjp1QRa9MaxKMxSvFTmJc+H1kXDLR+TGtUwcSfykxgPZJ+em48fzxdEaWuOF0X/hGvCr7SLYTxh9Gtk9AgW/IGrm+OhdhA0NKUAZT6EUQp1Is66ss= 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: Hi, Longlong, Longlong Xia writes: > We found that the plist_for_each_entry_safe() loop in get_swap_pages() > could reach tens of thousands of times to find available space (extreme > case: cond_resched() is not called in the loop). The test scenario is like > commit de1ccfb64824 ("swapfile: fix soft lockup in scan_swap_map_slots") > does. On the other hand, scan_swap_map_slots() needs to reach LATENCY_LIMIT > before calling cond_resched(), so cond_resched() is needed when failed to > find available space to avoid softlockup. Thanks for the patch. The patch itself looks good to me. I think that it's better to describe the test case in the patch description directly instead of referring the previous commit. Best Regards, Huang, Ying > Signed-off-by: Longlong Xia > --- > mm/swapfile.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 908a529bca12..4fa440e87cd6 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -1100,6 +1100,7 @@ int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size) > goto check_out; > pr_debug("scan_swap_map of si %d failed to find offset\n", > si->type); > + cond_resched(); > > spin_lock(&swap_avail_lock); > nextsi: