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[209.85.221.41]) by smtp.gmail.com with ESMTPSA id u23sm741998ejy.87.2020.10.14.06.35.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 14 Oct 2020 06:35:33 -0700 (PDT) Received: by mail-wr1-f41.google.com with SMTP id n6so3828480wrm.13; Wed, 14 Oct 2020 06:35:33 -0700 (PDT) X-Received: by 2002:a5d:5387:: with SMTP id d7mr5560989wrv.224.1602682533356; Wed, 14 Oct 2020 06:35:33 -0700 (PDT) MIME-Version: 1.0 References: <202010141228.09ECSg0D023438@repo.freebsd.org> In-Reply-To: From: Alexander Richardson Date: Wed, 14 Oct 2020 14:35:22 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: svn commit: r366697 - head/usr.bin/xinstall To: Mateusz Guzik Cc: src-committers , svn-src-all , svn-src-head Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 4CBD1z5BCFz40nw X-Spamd-Bar: - Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=none; spf=pass (mx1.freebsd.org: domain of arichardsonkde@gmail.com designates 209.85.218.65 as permitted sender) smtp.mailfrom=arichardsonkde@gmail.com X-Spamd-Result: default: False [-1.89 / 15.00]; RCVD_TLS_ALL(0.00)[]; FREEMAIL_ENVFROM(0.00)[gmail.com]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; R_SPF_ALLOW(-0.20)[+ip4:209.85.128.0/17]; NEURAL_HAM_LONG(-1.00)[-0.995]; MIME_GOOD(-0.10)[text/plain]; DMARC_NA(0.00)[freebsd.org]; ARC_NA(0.00)[]; RWL_MAILSPIKE_GOOD(0.00)[209.85.218.65:from]; RCVD_COUNT_THREE(0.00)[4]; TO_MATCH_ENVRCPT_SOME(0.00)[]; TO_DN_ALL(0.00)[]; NEURAL_HAM_SHORT(-0.12)[-0.122]; RCVD_IN_DNSWL_NONE(0.00)[209.85.218.65:from]; NEURAL_HAM_MEDIUM(-0.78)[-0.777]; FREEMAIL_TO(0.00)[gmail.com]; FORGED_SENDER(0.30)[arichardson@freebsd.org,arichardsonkde@gmail.com]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:15169, ipnet:209.85.128.0/17, country:US]; TAGGED_FROM(0.00)[]; FROM_NEQ_ENVFROM(0.00)[arichardson@freebsd.org,arichardsonkde@gmail.com]; MAILMAN_DEST(0.00)[svn-src-all,svn-src-head] X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 14 Oct 2020 13:35:36 -0000 On Wed, 14 Oct 2020 at 14:29, Mateusz Guzik wrote: > > This should use copy_file_range (also available on Linux). > I agree. I even mentioned this in https://reviews.freebsd.org/D26041#589287. This change avoids the two unnecessary syscalls, but I agree that longer-term install should share the copy_file_range code with cp. The only thing that copy_file_range won't speed up is the check whether source and target are already identical. Alex > On 10/14/20, Alex Richardson wrote: > > Author: arichardson > > Date: Wed Oct 14 12:28:41 2020 > > New Revision: 366697 > > URL: https://svnweb.freebsd.org/changeset/base/366697 > > > > Log: > > install(1): Avoid unncessary fstatfs() calls and use mmap() based on size > > > > According to git blame the trymmap() function was added in 1996 to skip > > mmap() calls for NFS file systems. However, nowadays mmap() should be > > perfectly safe even on NFS. Importantly, onl ufs and cd9660 file systems > > were whitelisted so we don't use mmap() on ZFS. It also prevents the use > > of mmap() when bootstrapping from macOS/Linux since on those systems the > > trymmap() function was always returning zero due to the missing > > MFSNAMELEN > > define. > > > > This change keeps the trymmap() function but changes it to check whether > > using mmap() can reduce the number of system calls that are required. > > Using mmap() only reduces the number of system calls if we need multiple > > read() > > syscalls, i.e. if the file size is > MAXBSIZE. However, mmap() is more > > expensive > > than read() so this sets the threshold at 4 fewer syscalls. Additionally, > > for > > larger file size mmap() can significantly increase the number of page > > faults, > > so avoid it in that case. > > > > It's unclear whether using mmap() is ever faster than a read with an > > appropriate > > buffer size, but this change at least removes two unnecessary system > > calls > > for every file that is installed. > > > > Reviewed By: markj > > Differential Revision: https://reviews.freebsd.org/D26041 > > > > Modified: > > head/usr.bin/xinstall/xinstall.c > > > > Modified: head/usr.bin/xinstall/xinstall.c > > ============================================================================== > > --- head/usr.bin/xinstall/xinstall.c Wed Oct 14 10:12:39 2020 (r366696) > > +++ head/usr.bin/xinstall/xinstall.c Wed Oct 14 12:28:41 2020 (r366697) > > @@ -148,7 +148,7 @@ static void metadata_log(const char *, const char *, s > > const char *, const char *, off_t); > > static int parseid(const char *, id_t *); > > static int strip(const char *, int, const char *, char **); > > -static int trymmap(int); > > +static int trymmap(size_t); > > static void usage(void); > > > > int > > @@ -1087,7 +1087,7 @@ compare(int from_fd, const char *from_name __unused, > > s > > if (do_digest) > > digest_init(&ctx); > > done_compare = 0; > > - if (trymmap(from_fd) && trymmap(to_fd)) { > > + if (trymmap(from_len) && trymmap(to_len)) { > > p = mmap(NULL, from_len, PROT_READ, MAP_SHARED, > > from_fd, (off_t)0); > > if (p == MAP_FAILED) > > @@ -1248,13 +1248,8 @@ copy(int from_fd, const char *from_name, int to_fd, > > co > > > > digest_init(&ctx); > > > > - /* > > - * Mmap and write if less than 8M (the limit is so we don't totally > > - * trash memory on big files. This is really a minor hack, but it > > - * wins some CPU back. > > - */ > > done_copy = 0; > > - if (size <= 8 * 1048576 && trymmap(from_fd) && > > + if (trymmap((size_t)size) && > > (p = mmap(NULL, (size_t)size, PROT_READ, MAP_SHARED, > > from_fd, (off_t)0)) != MAP_FAILED) { > > nw = write(to_fd, p, size); > > @@ -1523,20 +1518,23 @@ usage(void) > > * return true (1) if mmap should be tried, false (0) if not. > > */ > > static int > > -trymmap(int fd) > > +trymmap(size_t filesize) > > { > > -/* > > - * The ifdef is for bootstrapping - f_fstypename doesn't exist in > > - * pre-Lite2-merge systems. > > - */ > > -#ifdef MFSNAMELEN > > - struct statfs stfs; > > - > > - if (fstatfs(fd, &stfs) != 0) > > - return (0); > > - if (strcmp(stfs.f_fstypename, "ufs") == 0 || > > - strcmp(stfs.f_fstypename, "cd9660") == 0) > > - return (1); > > -#endif > > - return (0); > > + /* > > + * This function existed to skip mmap() for NFS file systems whereas > > + * nowadays mmap() should be perfectly safe. Nevertheless, using mmap() > > + * only reduces the number of system calls if we need multiple read() > > + * syscalls, i.e. if the file size is > MAXBSIZE. However, mmap() is > > + * more expensive than read() so set the threshold at 4 fewer syscalls. > > + * Additionally, for larger file size mmap() can significantly increase > > + * the number of page faults, so avoid it in that case. > > + * > > + * Note: the 8MB limit is not based on any meaningful benchmarking > > + * results, it is simply reusing the same value that was used before > > + * and also matches bin/cp. > > + * > > + * XXX: Maybe we shouldn't bother with mmap() at all, since we use > > + * MAXBSIZE the syscall overhead of read() shouldn't be too high? > > + */ > > + return (filesize > 4 * MAXBSIZE && filesize < 8 * 1024 * 1024); > > } > > _______________________________________________ > > svn-src-all@freebsd.org mailing list > > https://lists.freebsd.org/mailman/listinfo/svn-src-all > > To unsubscribe, send any mail to "svn-src-all-unsubscribe@freebsd.org" > > > > > -- > Mateusz Guzik