Date: Sat, 3 Sep 2022 06:26:27 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Rick Macklem <rmacklem@uoguelph.ca> Cc: FreeBSD Filesystems <freebsd-fs@freebsd.org> Subject: Re: RFC: multiple concurrent I/O ops for copy_file_range(2) Message-ID: <YxLJY47LWlEyk6gK@kib.kiev.ua> In-Reply-To: <YQXPR01MB41506C61D9936C01072F6373DD7D9@YQXPR01MB4150.CANPRD01.PROD.OUTLOOK.COM> References: <YQXPR01MB41506C61D9936C01072F6373DD7D9@YQXPR01MB4150.CANPRD01.PROD.OUTLOOK.COM>
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On Sat, Sep 03, 2022 at 03:11:03AM +0000, Rick Macklem wrote: > Hi, > > A recent discussion involving copy_file_range(2) performance > included a suggestion that, maybe, copying of subranges > should be done concurrently. > > Although I cannot be 100% sure, I think that this would > involve using multiple kernel threads (taskqueue or similar) > to issue I/O operations on the file system(s) for blocks > (of f_iosize maybe?) concurrently, to improve performance. > > Doing this in a system call is unusual, to say the least but, then, > copy_file_range(2) is an unusual system call to begin with. > > I have not attempted to code this up as of yet. > > So, what do others think of this idea? > Note that UFS does not understand more than one stream of writes to single vnode. The result could be a severe fragmentation, which is relevant even for SSDs (due to large internal block size).
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