From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=74.125.229.5 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794439265; b=qAm1wY8sSaS81ykeDWQpRZ0nueHNl4gLN2A9bxgHWOreoezGZ9ThIpIxmkjQs1rwZpSO sKGYY61tlQ/7ChsDhTkRT3239PvhPy+/bB1Mb37JjNZJfYW32jEL/OorlyqsLG99HVxe+ A7GokmVRQdKsP+Jx2WfNN1q3X7G0l0sscDpD7h7RJ99vWFc5XgjrRUZbgYeI/vpzek1D7 QjBBQVcRPDk4ZDbAixfwURbeacR/cyQfg7Kvpozbakrjn2DJY1cSLHKeqajLD9kfEt+FE bhAF62sB4BPPkpJFTabj7+G2hzeoeE4pf8OsV3VteDXO/CN90OV+3YbgdTmqsyoksvA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794439265; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Gm-Gg:X-Received:Received: Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:Content-Transfer-Encoding: In-Reply-To; bh=KNu4FBFo+NiXU4uk2EB8iN37f7AOkMfz2eB0q/Nmt5s=; b=bVth3voE7ObAirGw4mbKAiyO62N6TrTTLyHneZkVh3SY3ACQ0LROyV9KFEldSMgsLGCV U9rQPrhaF1npV2YpXLoGuCev+ta+4f1czQdMclgODAX3bgPWAwoJHrXatr2JtOIbT5WcT IcOlv5cgziMNgZOE8W/eod3AtVkcyF2v298E261+rpTZzqRrPJxbiTP1L/z2B5HufqGg5 PxBrLReXm/3wBwrfXqhPwWka9qd0FY6DAP98KoLuFxh+LAiKnSNQVttheTD9fngJujvZJ ltek+0vR0NG00BqhJbpJf+xll8WBmlMq1AbUJffVAEwFP9FTODMkjp9c5NVEJUyaciQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20260707 header.b=PG06NK+8; arc=none smtp.remote-ip=74.125.229.5 Received: from mail-dy2-f5.google.com (mail-dy2-f5.google.com [74.125.229.5]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7E09B60A2616 for ; Wed, 11 Nov 2026 23:21:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 7E09B60A2616 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20260707 header.b=PG06NK+8 Received: by mail-dy2-f5.google.com with SMTP id 5a478bee46e88-36caa19b0ffso2244925eec.0 for ; Wed, 11 Nov 2026 15:21:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20260707; t=1794439264; x=1795044064; darn=vger.kernel.org; h=in-reply-to:content-transfer-encoding:content-disposition :content-type:mime-version:references:message-id:subject:cc:to:from :date:from:to:cc:subject:date:message-id:reply-to:content-type; bh=KNu4FBFo+NiXU4uk2EB8iN37f7AOkMfz2eB0q/Nmt5s=; b=PG06NK+8sjeCnFGsPkv7biN/XWVPp8cx4Zvam/TsDYmOaiYK6pe/9gJPX+5xFQMDwG FI7ZSXarOy2ZHCcYR5HKV+yYkrekblBvCUk1vUXz8MBnle4pAyi/GaiRzj0Y8Nfhmwvr OtfaG8jT6g6qhd4JuBpdh076rXDErLVCFrVlN+o2mFB/qS+lMM/hs33G70qIsK6M4TEJ J9VDq8+u00RPZUP2ARQzoVo6UUoByewIDiHYnMAJTB80Wztg6WOV49S5nQpMmODo77Cm n18RFe/aTJZ38OOYzqUaC6AVSKP3D41+hpBAIqwtbHebYSyUXCxDDrF162O6k1hWddDh Thdg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1794439264; x=1795044064; h=in-reply-to:content-transfer-encoding:content-disposition :content-type:mime-version:references:message-id:subject:cc:to:from :date:x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to:content-type; bh=KNu4FBFo+NiXU4uk2EB8iN37f7AOkMfz2eB0q/Nmt5s=; b=vBtUsY1P6Pptz26GIHswxdpMh0kzTsxWZQjGcmTurDSEaFAvABJB3WWE4uYY7ZzTdZ UxhAHZ+dHDv9Tq6mZBADyUMpoW7EWZ3JqdnqRsRiRj/gOccH+jeQoL1AxXUejbEXwU/H bA1o9nSzaPmHWRBxfNuTaz33QQ3xPt2DGY81JPFtoYRxRW1UVr6XnljYGoakx0dhNGCW 0rQMniY97v0R/JZtxzzEM8KdS3WC5kaf7q/IzTIcTRO/TrtRjGRGIguUnMi7dyRAAxru LhcijrYDDN0K5Vh1vgGh8Z7ImfrQKEt6JfTHZS7K2pglDVy4KtRgQwbKGR2y4trvg+fL rLHQ== X-Forwarded-Encrypted: i=1; AL+hErE2ZzNEqepE6DXOV+qSe2tlD/T48nVAEWEk6HMlC08Ck6nuJzzLdgs2Y8y/U1Pvbm/R++1ZV4DvEmE=@vger.kernel.org X-Gm-Message-State: APuU4Z/5Psqus3S43l6KUk3CTYk1QZbhEifRPH1LFgxvOt2XVv7YCJwe 7XXljYoS/82G1UKCeIqhqcqgsAxcu4fcbnfgaz00Pwy1p/uHjIHuR2nx X-Gm-Gg: AYBFou2he1yZyzPK7QgIZlgiJ9vG01zSy+rlH7z82FI8Y1YF3me6DrJ9WhqQ4/Gw1gj /QYsmpJjvJ1SzwHh/igFw0MHvEAzKRB+UEQIeAnvO0ir6izgiaYmkPbfaqBmBuNlRK8cQ0epFqU NedvK5toDG4UqJFsL1LL4J0IaWJM5FQcdgw4vSsyef3qW9BbL+FmbC+QmQh2lA9Q6L+k20fXTzg 1KFgIQFONvOeDAUoXAO4P29RJqVAK7WNwBS/Gk5bUF72weSCRolxozesIK5M+OXRqg+P39JTjd5 0KhuksxuLQi/miWkqZN8mwgu/VWGuwagR564RMThb2rUGKKrbmADmc68sBMLuBJ7RZQqkRgfQCm JUZR14umLnKvyqWUJKBQ9Lmx/zbBGm0u8cDiFhQEkXkKc56stQZM3oComsGT555Vkqr83eCb5cK HCgKUDJ9UOEw0H3jDjwGNazd8SntDEeq0go/EVkPXV7W44LWuOjOOmNGrZRtUMjhiVGQNFDrl8R xhPsygSL4QPKVp3ZknMAmZ2VTOB9YAPydGmSLmvqKdYhQiEbDLaltGqSf0LgpgdcWfAV5d2P4rK oxZ4EAKnds7i6uks2wNBaGM= X-Received: by 2002:a05:7300:fc13:b0:375:87f5:ccee with SMTP id 5a478bee46e88-37686a456b0mr3993699eec.29.1794439264317; Wed, 11 Nov 2026 15:21:04 -0800 (PST) Received: from localhost ([2a03:2880:9ff:67::]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-37520bf3e18sm39819238eec.16.2026.11.11.15.21.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Nov 2026 15:21:03 -0800 (PST) Date: Wed, 11 Nov 2026 15:09:21 -0800 From: Stanislav Fomichev To: =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= Cc: Magnus Karlsson , Maciej Fijalkowski , Stanislav Fomichev , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Jonathan Corbet , Shuah Khan , Randy Dunlap , Alexander Duyck , kernel-team@meta.com, Andrew Lunn , Jesper Dangaard Brouer , Ilias Apalodimas , Alexei Starovoitov , Daniel Borkmann , John Fastabend , Pavel Begunkov , Jens Axboe , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Ihor Solodrai , netdev@vger.kernel.org, bpf@vger.kernel.org, io-uring@vger.kernel.org, Mina Almasry , "Mike Marciniszyn (Meta)" , Weiming Shi , Nikolay Aleksandrov , David Wei , Alexander Lobakin , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Stuart Clark Subject: Re: [PATCH net-next v1 04/11] xsk: Allocate UMEM chunks through page_pool Message-ID: References: <20261110102039.1002605-1-bjorn@kernel.org> <20261110102039.1002605-5-bjorn@kernel.org> <87o6bv8o5e.fsf@all.your.base.are.belong.to.us> X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87o6bv8o5e.fsf@all.your.base.are.belong.to.us> On 11/11, Björn Töpel wrote: > Stanislav Fomichev writes: > > > On 11/10, Björn Töpel wrote: > > >> diff --git a/net/xdp/xsk_pp.c b/net/xdp/xsk_pp.c > >> new file mode 100644 > >> index 000000000000..fdd55265a6cd > >> --- /dev/null > >> +++ b/net/xdp/xsk_pp.c > >> @@ -0,0 +1,246 @@ > >> +// SPDX-License-Identifier: GPL-2.0 > >> +/* AF_XDP UMEM as a page pool memory provider > >> + * > >> + * Each aligned UMEM chunk is a readable net_iov with one owner at a time: > >> + * > >> + * userspace --FILL--> page pool --release--> reuse --alloc--> page pool > >> + * ^ | > >> + * +-----RX ring-------+ > >> + */ > >> + > >> +#include > >> +#include > >> +#include > >> + > >> +#include "xsk.h" > >> +#include "xsk_queue.h" > >> + > >> +enum xsk_pp_chunk { > >> + XSK_PP_USER, /* owned by userspace */ > >> + XSK_PP_POOL, /* owned by a page pool */ > >> + XSK_PP_REUSE, /* on the reuse stack */ > > > > Can you explain more about that reuse/reuse_cnt? When is the chunk reused? > > How is it different from FILL->RX path? > > > FILL RX ring > USER ----------> POOL ---------------> USER > | ^ > release_netmem | | next refill, > v | before FILL > REUSE > > POOL is a chunk in the page pool or on a driver ring. XDP_DROP, copied > XDP_PASS and XDP_TX recycle it inside the page pool, so it stays POOL. > FILL->RX is the only way back to userspace: an XSK redirect puts the > chunk on the RX ring, and the flush (patch 7) marks it USER. Userspace > posts it to FILL again. > > REUSE is a chunk the page pool lets go of without a packet: when the > pool is destroyed (queue restart, unbind), or its ring is full on a > recycle. Userspace already gave it up, and the kernel can't post to > FILL, so the next refill takes it before FILL. Same job as free_list in > xsk_buff_pool. A FILL entry for a chunk the kernel holds is dropped. > > I'll put that in the comment at the top of xsk_pp.c. Yes, that helps a lot, thanks!