Re: limit for mmaping for readfile (Bug #19749)

Andi, Do you think mmap'ing a series of smaller chunks is going to be faster than mmap'ing the whole file, or faster than reading chunks conventionally? (just asking; I've not done any tests) The mmap code in the passthru function will fall back on reading chunks in a loop if the mmap failed. The proposed mmap limit really just a runaway brake to avoid the box swapping to death if, say, 5 people start downloading 5 .iso images through a PHP script using readfile(). My patch is "nice" at this stage in the release because it is a minimal change that can't hurt anything; tweaking the passthru code is a bit more worrying :/ --Wez. ----- Original Message ----- From: "Andi Gutmans" <andi@zend.com> To: "Wez Furlong" <wez@thebrainroom.com>; <internals@lists.php.net> Sent: Wednesday, April 21, 2004 10:52 AM Subject: Re: [PHP-DEV] limit for mmaping for readfile (Bug #19749) > Wez, > > I have played with mmap() in the past. I found that mapping in relatively > small blocks such as 1MB does not really hurt performance. I suggest not to > add yet another INI option but to do it with smaller blocks. I think even > 256KB wouldn't make a big difference. > > Andi > > At 10:10 PM 4/20/2004 +0100, Wez Furlong wrote: > >http://bugs.php.net/bug.php?id=19749 > > > >It's been playing on my mind recently that this bug > >hasn't been addressed; the problem was how to guess > >precisely what limit to set for mmaping when doing > >something like readfile(). > >[note that some comments are missing from the bugdb > >for that bug] > > > >Well, we can solve the problem by allowing the > >sysadmin to decide, as you can see in my patch > >against PHP 5: > > > >http://www.php.net/~wez/mmap-limit.diff > > > >The default limit is 8MB. If the limit is set to 0, > >no limit is applied. > > > >This is separate from memory_limit, so PHP could > >potentially use double the default memory amount for a > >short period of time. This is still better than allowing > >it to eat all the RAM when someone decides to readfile() > >large media files for example. > > > >--Wez. > > > >-- > >PHP Internals - PHP Runtime Development Mailing List > >To unsubscribe, visit: http://www.php.net/unsub.php > > > >