On Thu, Feb 24, 2011 at 02:13:35PM -0800, Andrew Morton wrote: > On Thu, 24 Feb 2011 14:10:34 -0800 > Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > > On Tue, 22 Feb 2011 21:17:04 +0100 > > Petr Holasek <pholasek@xxxxxxxxxx> wrote: > > > > > When user insert negative value into /proc/sys/vm/nr_hugepages it will > > > result > > > in the setting a random number of HugePages in system > > > > Is this true? afacit the kernel will allocate as many pages as it can > > and will then set /proc/sys/vm/nr_hugepages to reflect the result. > > That's not random. > > > > Assuming the above to be correct, I altered the changelog thusly: > AFAIK, it's correct. > : When the user inserts a negative value into /proc/sys/vm/nr_hugepages it > : will cause the kernel to allocate as many hugepages as possible and to > : then update /proc/meminfo to reflect this. > : > : This changes the behavior so that the negative input will result in > : nr_hugepages value being unchanged. > > and given that, I don't really see why we should change the existing behaviour. > The main motivation is that asking the kernel for -1 pages and getting a sensible response just feels wrong. The second reason I'd guess is that an administrator script that was buggy (or raced with a second) instance that accidentally wrote a negative number to the proc interface would try allocating all memory as huge pages instead of reducing the number of hugepages as was probably intended. Totally hypothetical case of course, I haven't actually heard of this happening to anyone. -- Mel Gorman SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>