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Miller" , cgroups@vger.kernel.org, linux-mm@kvack.org, Roman Gushchin Subject: Re: [PATCH net-next] net-memcg: pass in gfp_t mask to mem_cgroup_charge_skmem() Message-ID: <20221012204941.3223d205@kernel.org> In-Reply-To: References: <20210817194003.2102381-1-weiwan@google.com> <20221012163300.795e7b86@kernel.org> <20221012173825.45d6fbf2@kernel.org> <20221013005431.wzjurocrdoozykl7@google.com> <20221012184050.5a7f3bde@kernel.org> <20221012201650.3e55331d@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="Unfvd/ba"; spf=pass (imf15.hostedemail.com: domain of kuba@kernel.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=kuba@kernel.org; dmarc=pass (policy=none) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1665632986; a=rsa-sha256; cv=none; b=FyU0x5nzWboX8+zxTlKoJ5TazCGYxEadQWrNJiA5Y1y8tAqpOvbJxm8lgdnSIvlx6Gfb7q eaXfY4ERJX17D9OVcyFLfR2+uiSHHl3pldmnXPdy49GTxQ30gek7D1gjcTFw5ntnGGukvu /2tqWmPWFISyiWTjPOKkbNkpe+20l8c= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1665632986; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=TDoAvmxqDivmZDA9R6kNxpewshbVsLD3zznf7oE+0go=; b=zlcfA/6SSyzlXFb9HX0Cb0qHZdL17Y3TsuX+x3zLx/D19HIDgAlk6cGI/6wzxGcTaOi69q zV/uq/wVLOBdiL/0WY9BB7t7TunXCXq3p/cgxKbzXE3wdUdyTmySUxwp3iZIcXm6/OjcZs SL8Upi24WYEaKRf2HKIukJG/gP6wlFM= X-Rspamd-Queue-Id: 2090BA0027 X-Rspam-User: Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="Unfvd/ba"; spf=pass (imf15.hostedemail.com: domain of kuba@kernel.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=kuba@kernel.org; dmarc=pass (policy=none) header.from=kernel.org X-Rspamd-Server: rspam04 X-Stat-Signature: 6k367mn58677z4bc1dpgss9ue4odjbzj X-HE-Tag: 1665632985-296626 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 Wed, 12 Oct 2022 20:34:00 -0700 Wei Wang wrote: > > I pushed this little nugget to one affected machine via KLP: > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 03ffbb255e60..c1ca369a1b77 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -7121,6 +7121,10 @@ bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages, > > return true; > > } > > > > + if (gfp_mask == GFP_NOWAIT) { > > + try_charge(memcg, gfp_mask|__GFP_NOFAIL, nr_pages); > > + refill_stock(memcg, nr_pages); > > + } > > return false; > > } > > > AFAICT, if you force charge by passing __GFP_NOFAIL to try_charge(), > you should return true to tell the caller that the nr_pages is > actually being charged. Ack - not sure what the best thing to do is, tho. Always pass NOFAIL in softirq? It's not clear to me yet why doing the charge/uncharge actually helps, perhaps try_to_free_mem_cgroup_pages() does more when NOFAIL is passed? I'll do more digging tomorrow. > Although I am not very sure what refill_stock() does. Does that > "uncharge" those pages? I think so, I copied it from mem_cgroup_uncharge_skmem().