Jose Mª Ferreiro wrote: > Andrei Martynov escribió: > >I'm using kernel 2.6.24 with uClinux and ARM NOMMU patches. When one > >application starts reading from disk kernel uses all available memory > >for caching and other applications fail to start (not enough memory). > >It takes kernel up to 10 seconds to release memory after the first > >application exits. > > > >Is there any way to limit disk cache size? > >... > > Hello > > I came to his thread because we had a similar issue: applications didn´t > start or start badly because system fails out of memory. I have not > found any reference to how to set that limit. It seems as if it works > that way: no limit; the mm system decides when and how :-(
The problem is fragmentation, not running out of memory, and it's quite difficult to solve. Limiting the cache sizes could help but it's not enough by itself - you also need to cluster cache memories, and limit the size more rigidly than mm's default async method. Otherwise even a small amount of cache gets spread randomly through memory and blocks large allocations. The kernel does have a strategy for this - look at migrationtype and pageblock in mm/*.c, but it seems to be not effective enough for small RAM sizes and NOMMU allocation patterns. The 10 second time is due to the mm/ strategy not working very well. > We are working with this workaround: > echo 3 > /proc/sys/vm/drop_caches > > This clears all the cache. We even write this value to that file within > our application start routine to be sure our main application gets all > the memory it needs. It seems to be working It's good to know that works, thanks. Another trick is to divide your application into several shared libraries which are significantly smaller than the original, if your toolchain supports it. -- Jamie _______________________________________________ uClinux-dev mailing list uClinux-dev@uclinux.org http://mailman.uclinux.org/mailman/listinfo/uclinux-dev This message was resent by uclinux-dev@uclinux.org To unsubscribe see: http://mailman.uclinux.org/mailman/options/uclinux-dev
