From nobody Thu Jul 25 21:11:22 2024 X-Original-To: freebsd-hackers@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4WVNq31cRPz5RKTh for <freebsd-hackers@mlmmj.nyi.freebsd.org>; Thu, 25 Jul 2024 21:11:27 +0000 (UTC) (envelope-from jake@technologyfriends.net) Received: from ci74p00im-qukt09090501.me.com (ci74p00im-qukt09090501.me.com [17.57.156.22]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4WVNq26xNfz4G0N for <freebsd-hackers@freebsd.org>; Thu, 25 Jul 2024 21:11:26 +0000 (UTC) (envelope-from jake@technologyfriends.net) Authentication-Results: mx1.freebsd.org; none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=technologyfriends.net; s=sig1; t=1721941885; bh=miwWTOTo4TOzWgG4TNgpUhVhQhtkNzkYMcQBBEeMLz4=; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; b=jcSfAQ8hop1AV80Se9K4M50/r++4spR48NTz4ewVwc6b3gNg+KvUUYtnN4pJj1iGf XUyuwhj3Y4H7f0pGK3P11HmHxzeeYoUU4qs8GCE6XUVabr1iDhwi0zyOBoY7JwR7Vf OYfszJTEAvANaLQttTVUgkzk7ZnI0ijlyf3aiWjqjQLA/28b/+epb7h+SC7CZ3sjfP hsxI2/srfKuXFKR6dawP688XFXNyBrt5iZRDQrI2f6ymFfbv8Quvfg54x0Q4UnvBo9 /qp+BscbEBKlxqKm3SOs5BQzc7/TRkU+kiHfjCV8SSpifJPlSr36LvPME9Hy3gQrv0 Rj5DcVMCdo0iQ== Received: from [10.0.233.209] (ci77p00im-dlb-asmtp-mailmevip.me.com [17.57.156.26]) by ci74p00im-qukt09090501.me.com (Postfix) with ESMTPSA id 4201D46401FD; Thu, 25 Jul 2024 21:11:24 +0000 (UTC) Message-ID: <4d4398e5-81ba-4fbd-9806-649ec70abdb4@technologyfriends.net> Date: Thu, 25 Jul 2024 16:11:22 -0500 List-Id: Technical discussions relating to FreeBSD <freebsd-hackers.freebsd.org> List-Archive: https://lists.freebsd.org/archives/freebsd-hackers List-Help: <mailto:freebsd-hackers+help@freebsd.org> List-Post: <mailto:freebsd-hackers@freebsd.org> List-Subscribe: <mailto:freebsd-hackers+subscribe@freebsd.org> List-Unsubscribe: <mailto:freebsd-hackers+unsubscribe@freebsd.org> Sender: owner-freebsd-hackers@FreeBSD.org MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: FreeBSD hugepages To: Mark Johnston <markj@freebsd.org> Cc: Konstantin Belousov <kostikbel@gmail.com>, freebsd-hackers@freebsd.org References: <1ced4290-4a31-4218-8611-63a44c307e87@technologyfriends.net> <ZqKhP0aR0fb_f6XE@kib.kiev.ua> <35da66f9-b913-45ea-90f4-16a2fa072848@technologyfriends.net> <ZqKzCK4pHg1mrSOa@nuc> Content-Language: en-US From: Jake Freeland <jake@technologyfriends.net> In-Reply-To: <ZqKzCK4pHg1mrSOa@nuc> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Proofpoint-GUID: e_CfyNCBo8I2LLM_8NiIBs3OBGYI2-85 X-Proofpoint-ORIG-GUID: e_CfyNCBo8I2LLM_8NiIBs3OBGYI2-85 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-07-25_21,2024-07-25_03,2024-05-17_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 phishscore=0 suspectscore=0 malwarescore=0 mlxscore=0 spamscore=0 bulkscore=0 mlxlogscore=999 clxscore=1030 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2308100000 definitions=main-2407250145 X-Spamd-Bar: ---- X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[]; ASN(0.00)[asn:714, ipnet:17.57.156.0/24, country:US] X-Rspamd-Queue-Id: 4WVNq26xNfz4G0N On 7/25/24 15:18, Mark Johnston wrote: > On Thu, Jul 25, 2024 at 02:47:16PM -0500, Jake Freeland wrote: >> On 7/25/24 14:02, Konstantin Belousov wrote: >>> On Thu, Jul 25, 2024 at 01:46:17PM -0500, Jake Freeland wrote: >>>> Hi there, >>>> >>>> I have been steadily working on bringing Data Plane Development Kit (DPDK) >>>> on FreeBSD up to date with the Linux version. The most significant hurdle so >>>> far has been supporting concurrent DPDK processes, each with their own >>>> contiguous memory regions. >>>> >>>> These contiguous regions are used by DPDK as a heap for allocating DMA >>>> buffers and other miscellaneous resources. Retrieving the underlying memory >>>> and mapping these regions is currently different on Linux and FreeBSD: >>>> >>>> On Linux, hugepages are fetched from the kernel's pre-allocated hugepage >>>> pool and are mapped into virtual address space on DPDK initialization. Since >>>> the hugepages exist in a pool, multiple processes can reserve their own >>>> hugepages and operate concurrently. >>>> >>>> On FreeBSD, DPDK uses an in-house contigmem kernel module that reserves a >>>> large contiguous region of memory on load. During DPDK initialization, the >>>> entire region is mapped into virtual address space. This leaves no memory >>>> for another independent DPDK process, so only one process can operate at a >>>> time. >>>> >>>> I could modify the DPDK contigmem module to mimic Linux's hugepages, but I >>>> thought it would be better to integrate and upstream a hugepage-like >>>> interface directly in the FreeBSD kernel source. I am writing this email to >>>> see if anyone has any advice on the matter. I did not see any previous >>>> attempts at this in Phabriactor or the commit log, but it is possible that I >>>> missed it. I have read about transparent superpage promotion, but that seems >>>> like a different mechanism altogether. >>>> >>>> At a quick glance, the implementation seems straightforward: read some >>>> loader tunables, allocate persistent hugepages at boot time, and create a >>>> pseudo filesystem that supports creating and mapping hugepages. I could be >>>> underestimating the magnitude of this task, but that is why I'm asking for >>>> thoughts and advice :) >>>> >>>> For reference, here is Linux's documentation on hugepages: >>>> https://docs.kernel.org/admin-guide/mm/hugetlbpage.html >>> Are posix shm largepages objects enough (they were developed to support >>> DPDK). Look for shm_create_largepage(3). >> Yes, shm_create_largepage(2) looks promising, but I would like the ability >> to allocate these largepages at boot time when memory fragmentation as at a >> minimum. Perhaps a couple sysctl tunables could be added onto the >> vm.largepages node to specify a pagesize and allocate some number of pages >> at boot? > We could add an rc script which creates named largepage objects. This > can be done using the posixshmcontrol utility. That might not be early > enough during boot for some purposes. In that case, we could have a > module which creates such objects from within the kernel. This is > pretty straightforward to do; I wrote a dumb version of this for a > mips-specific project a few years ago, feel free to take code or > inspiration from it: https://people.freebsd.org/~markj/tlbdemo.c Looks simple enough. Thanks for the example code. >> It seems Linux had an interface similar to shm_create_largepage(2) back in >> v2.5, but they removed it in favor of their hugetlbfs filesystem. It would >> be nice to stay close to the file-backed Linux interface to maximize code >> sharing in userspace. It looks like the foundation for hugepages is there, >> but the interface for allocation and access needs to be extended. > POSIX shm objects have most of the properties one would want, I'd > expect, save the ability to access them via standard syscalls. What > else is missing besides the ability to reserve memory at boot time? Most notably, I would like the ability to allocate pages in a specific NUMA domain. Otherwise, in a perfect world, I'd like a unified interface for both Linux and FreeBSD. Linux hugepages are managed using standard system calls; files are mmap(2)'d into virtual address space from hugetlbfs and ftruncate(2)'d. A matching interface would not add an extra kernel entrypoint and even more importantly, it would ease the Linux-to-FreeBSD porting process for programs that use hugepages. Thanks, Jake Freeland