From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2E130C636CC for ; Wed, 8 Feb 2023 01:57:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A317F6B0071; Tue, 7 Feb 2023 20:56:59 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9E0B76B0072; Tue, 7 Feb 2023 20:56:59 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8A9CB6B0073; Tue, 7 Feb 2023 20:56:59 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 798436B0071 for ; Tue, 7 Feb 2023 20:56:59 -0500 (EST) Received: from smtpin09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 54694A0859 for ; Wed, 8 Feb 2023 01:56:59 +0000 (UTC) X-FDA: 80442461358.09.4406019 Received: from mail-ed1-f49.google.com (mail-ed1-f49.google.com [209.85.208.49]) by imf21.hostedemail.com (Postfix) with ESMTP id 8B61A1C000A for ; Wed, 8 Feb 2023 01:56:57 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=ZbHvqK6w; spf=pass (imf21.hostedemail.com: domain of alexei.starovoitov@gmail.com designates 209.85.208.49 as permitted sender) smtp.mailfrom=alexei.starovoitov@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1675821417; 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=qWswHjZfE/NK5HNFXHCk8eijOrRMtyo/H4dKw814SU8=; b=sYIhGkvHzZ0hduI/YPn5weNNBzW1Zo3uADPZVxhPmZzdK14HVQ4rxjFDYboyYXS5SjyeaW y7CgM+H+Ic6e30UPpEYiZ9OISFWXBmHNQtiWRMM2OBIwVAyhF9yB996Q+OuUHYdW7z5QxG W4pPx8mcvNG/1uxlIMrTjl0XsiKLPlU= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=ZbHvqK6w; spf=pass (imf21.hostedemail.com: domain of alexei.starovoitov@gmail.com designates 209.85.208.49 as permitted sender) smtp.mailfrom=alexei.starovoitov@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1675821417; a=rsa-sha256; cv=none; b=xA7W9y3ZUROZsvIp84xjuTfUSGqujQxRQ6y1VnDfNeBYuNaVxv/haB4NzfSFoa/OaxzlFr H3rCPDmSkAoPgVSQbCqqi9TaLj5L0LgPyUIhj03L2e/0fkUft+SksCc1urFSls86+Q/pGZ 90OTWXNsZNqnkMo8m41LsI7lhv2+Ixs= Received: by mail-ed1-f49.google.com with SMTP id a10so11517599edu.9 for ; Tue, 07 Feb 2023 17:56:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=qWswHjZfE/NK5HNFXHCk8eijOrRMtyo/H4dKw814SU8=; b=ZbHvqK6wX37Ta0NG9nFt6fT5/XJnSgbf2oZofuDgCIXWz/LT/Kum6ALV4PFDX1CgmN EYNic2FFeCRUrAts5tevK3SWhnLMMHk98/67N2dJcKGNJL7YnXs3MLpHOiGUL+Axj7+1 6xoW1gfPPDZTVmMg/2zfdhSXMPSnVBSxxBEoDV5oxtG2GEmwy61ku7w8TULzHJbCVIEW vhBVWRRswll0niz1+gY7wW8eNxmn55cW/7iKXp4Ps7W6W9qnL7Dv2T7w0AjMjlbrhAPF J3+Qzkn5QdqA6tD797T1KeRhtKmNETCfaAi+76lHNpsyDF5qLTmAK9Ec9lXwMgdcvBZD 5wFw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=qWswHjZfE/NK5HNFXHCk8eijOrRMtyo/H4dKw814SU8=; b=mPyDJdFbFX8kWrSeiv+DrreRAVFGpDnTcLgGllxClf4PyzdJEWmj+a4OoOxQ7QQcxl 0CiFFbAvcb6hCEqZX/gljoU8AjbBH4pxaOGdM9JQuT1SH/2YlP767HGRZF8ajOpCcX8w GHso+J/M1+X1S9Zd7rKl6Do8GangheGFO+6hWtFlTxOxQNb6TO/amOhcj5aKdOnf93F8 kNho7gXixPrVuy3wfgeOx5O9aNp/owry/7fvoVtk5oTvn4yC/y/Tf1J9teCDr0QQ9tEF PK+hUAKOUU2sQKcTEXcoSxcODdgaY1azFsLvHAlOULZg92TaIs3hMh6aNuWPaVFIOtm2 4c/g== X-Gm-Message-State: AO0yUKX+rJuuXMUW0AqHNRm4J3RwXpaV8oOBnDuU5zjT1+eflMx2CGXZ 7kg88URVmw0K6t3tmxhioFlYheqpnPOQLvnB4pI= X-Google-Smtp-Source: AK7set8Doz0Ia4La/kfFSzyiw+nXXjNGhS9r4tzNLD9CCqrGA8VDWhvXPL81940RyPC1UjGFQj/A5oa3eDS9BKmTcGk= X-Received: by 2002:a50:9ecb:0:b0:49d:ec5d:28b4 with SMTP id a69-20020a509ecb000000b0049dec5d28b4mr1187168edf.6.1675821415834; Tue, 07 Feb 2023 17:56:55 -0800 (PST) MIME-Version: 1.0 References: <20230202014158.19616-1-laoar.shao@gmail.com> <20230202014158.19616-8-laoar.shao@gmail.com> <63ddbc69ef50f_6bb1520813@john.notmuch> In-Reply-To: From: Alexei Starovoitov Date: Tue, 7 Feb 2023 17:56:44 -0800 Message-ID: Subject: Re: [PATCH bpf-next 7/7] bpf: hashtab memory usage To: Yafang Shao Cc: John Fastabend , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Tejun Heo , dennis@kernel.org, Chris Lameter , Andrew Morton , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Vlastimil Babka , urezki@gmail.com, linux-mm , bpf Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 8B61A1C000A X-Stat-Signature: qxid96pxncqeaqoncw1cxfcrm9qzemhc X-HE-Tag: 1675821417-829585 X-HE-Meta: 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 tNAbqFev opMDDrdJDTEEnj7aGR4EON9KXMk3RtXZPjK8ETgfi4p4LgH5DzIwpIumb1lquS3VzTBEWrp6v0tKgZXlnbuhU1VvtV8nbVaRzBrNmQpEJa5rTHFxfDIfXNm0Oce9UVoYeZqQiyTmDh23HmVZSGMG2wjJyozIqEbLjrjNKYW9oQecGWHJ/t8dWsRIRzFJjKLFaoPxBUFTJk1K0Dfc0w3CLK7MzMqQQdjkuCyQAgr83fkn5vRED6F9RsI8JFfl7bkqES2hMvxbOpJ/7q/d8gk/AqHGM46p0z31MRSvgMqcASxX282UyTLbYcV+RePYa+zfobr4MVfe2Z7N5FJR4X1lV8ndpwRB4eQJUYMB1voLVjBCoijmDC1Iov0+/K7Aggr4MTuvBfxoHkpKYrXglz+67SrZO16CBCkpdCvZBTQcCPzmhcYl+HO9M1GL2KgX8IVi/1hn56C3GdcJiCvB+IlItQLMcoE/7MUiYMghN81IY/IAf8gPqK6uhXfQrIg== 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 Sat, Feb 4, 2023 at 7:56 PM Yafang Shao wrote: > > On Sat, Feb 4, 2023 at 10:01 AM John Fastabend = wrote: > > > > Yafang Shao wrote: > > > Get htab memory usage from the htab pointers we have allocated. Some > > > small pointers are ignored as their size are quite small compared wit= h > > > the total size. > > > > > > The result as follows, > > > - before this change > > > 1: hash name count_map flags 0x0 <<<< prealloc > > > key 16B value 24B max_entries 1048576 memlock 41943040B > > > 2: hash name count_map flags 0x1 <<<< non prealloc, fully set > > > key 16B value 24B max_entries 1048576 memlock 41943040B > > > 3: hash name count_map flags 0x1 <<<< non prealloc, non set > > > key 16B value 24B max_entries 1048576 memlock 41943040B > > > > > > The memlock is always a fixed number whatever it is preallocated or > > > not, and whatever the allocated elements number is. > > > > > > - after this change > > > 1: hash name count_map flags 0x0 <<<< prealloc > > > key 16B value 24B max_entries 1048576 memlock 109064464B > > > 2: hash name count_map flags 0x1 <<<< non prealloc, fully set > > > key 16B value 24B max_entries 1048576 memlock 117464320B > > > 3: hash name count_map flags 0x1 <<<< non prealloc, non set > > > key 16B value 24B max_entries 1048576 memlock 16797952B > > > > > > The memlock now is hashtab actually allocated. > > > > > > At worst, the difference can be 10x, for example, > > > - before this change > > > 4: hash name count_map flags 0x0 > > > key 4B value 4B max_entries 1048576 memlock 8388608B > > > > > > - after this change > > > 4: hash name count_map flags 0x0 > > > key 4B value 4B max_entries 1048576 memlock 83898640B > > > > > > > This walks the entire map and buckets to get the size? Inside a > > rcu critical section as well :/ it seems. > > > > No, it doesn't walk the entire map and buckets, but just gets one > random element. > So it won't be a problem to do it inside a rcu critical section. > > > What am I missing, if you know how many elements are added (which > > you can track on map updates) how come we can't just calculate the > > memory size directly from this? > > > > It is less accurate and hard to understand. Take non-preallocated > percpu hashtab for example, > The size can be calculated as follows, > key_size =3D round_up(htab->map.key_size, 8)=EF=BC=9B > value_size =3D round_up(htab->map.value_size, 8); > pcpu_meta_size =3D sizeof(struct llist_node) + sizeof(void *); > usage =3D ((value_size * num_possible_cpus() +\ > pcpu_meta_size + key_size) * max_entries > > That is quite unfriendly to the newbies, and may be error-prone. Please do that instead. map_mem_usage callback is a no go as I mentioned earlier. > Furthermore, it is less accurate because there is underlying memory > allocation in the MM subsystem. > Now we can get a more accurate usage with little overhead. Why not do it? because htab_mem_usage() is not maintainable long term. 100% accuracy is a non-goal.