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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 339B0C43334 for ; Sun, 12 Jun 2022 07:30:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234591AbiFLHaO (ORCPT ); Sun, 12 Jun 2022 03:30:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34752 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229559AbiFLHaN (ORCPT ); Sun, 12 Jun 2022 03:30:13 -0400 Received: from out2.migadu.com (out2.migadu.com [IPv6:2001:41d0:2:aacc::]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D734A39172 for ; Sun, 12 Jun 2022 00:30:10 -0700 (PDT) Message-ID: <4980fd4d-b1f3-7b1c-8bfc-6be4d31f9da0@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1655019009; h=from:from: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; bh=3Jf+WCty4UwT2ti01UMmYuZdJvo2wax71H3TJg5XTAI=; b=XxuOiDYAcSUgCKvZWtixYgCSt7jYu1/xRDY6BfHDeMGNlcM07sPDoj5TBGn/4102ydDauB hKzvipCSBAdRGVqfUvgORrgmRKWOt/o0y381Wxbo8wBqtGClV8c6K7DJBac5UDZvqc8jx8 09eBi5GBCbeZSqP1hem6lEKwduc+Lyc= Date: Sun, 12 Jun 2022 15:30:01 +0800 MIME-Version: 1.0 Subject: Re: [RFC] support memory recycle for ring-mapped provided buffer Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Hao Xu To: io-uring Cc: Jens Axboe , Pavel Begunkov References: <6641baea-ba35-fb31-b2e7-901d72e9d9a0@linux.dev> In-Reply-To: <6641baea-ba35-fb31-b2e7-901d72e9d9a0@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 6/10/22 13:55, Hao Xu wrote: > Hi all, > > I've actually done most code of this, but I think it's necessary to > first ask community for comments on the design. what I do is when > consuming a buffer, don't increment the head, but check the length > in real use. Then update the buffer info like > buff->addr += len, buff->len -= len; > (off course if a req consumes the whole buffer, just increment head) > and since we now changed the addr of buffer, a simple buffer id is > useless for userspace to get the data. We have to deliver the original > addr back to userspace through cqe->extra1, which means this feature > needs CQE32 to be on. > This way a provided buffer may be splited to many pieces, and userspace > should track each piece, when all the pieces are spare again, they can > re-provide the buffer.(they can surely re-provide each piece separately > but that causes more and more memory fragments, anyway, it's users' > choice.) > > How do you think of this? Actually I'm not a fun of big cqe, it's not > perfect to have the limitation of having CQE32 on, but seems no other > option? > > Thanks, > Hao To implement this, CQE32 have to be introduced to almost everywhere. For example for io_issue_sqe: def->issue(); if (unlikely(CQE32)) __io_req_complete32(); else __io_req_complete(); which will cerntainly have some overhead for main path. Any comments? Regards, Hao