On 04/02/2012 07:10 PM, KOSAKI Motohiro wrote: > 2012/3/30 Satoru Moriya <satoru.moriya@xxxxxxx>: >> Hello Kosaki-san, >> >> On 03/07/2012 01:18 PM, Satoru Moriya wrote: >>> On 03/07/2012 12:19 PM, KOSAKI Motohiro wrote: >>>> Thank you. I brought back to memory it. Unfortunately DB folks are >>>> still mainly using RHEL5 generation distros. At that time, >>>> swapiness=0 doesn't mean disabling swap. >>>> >>>> They want, "don't swap as far as kernel has any file cache page". but >>>> linux don't have such feature. then they used swappiness for emulate >>>> it. So, I think this patch clearly make userland harm. Because of, we >>>> don't have an alternative way. >> >> As I wrote in the previous mail(see below), with this patch >> the kernel begins to swap out when the sum of free pages and >> filebacked pages reduces less than watermark_high. Actually, this is true only for global reclaims. Reclaims in cgroup can fail in this case. >> >> So the kernel reclaims pages like following. >> >> nr_free + nr_filebacked >= watermark_high: reclaim only filebacked pages >> nr_free + nr_filebacked < watermark_high: reclaim only anonymous pages > > How? get_scan_count() checks that case explicitly: if (global_reclaim(sc)) { free = zone_page_state(mz->zone, NR_FREE_PAGES); /* If we have very few page cache pages, force-scan anon pages. */ if (unlikely(file + free <= high_wmark_pages(mz->zone))) { fraction[0] = 1; fraction[1] = 0; denominator = 1; goto out; } } Regards, Jerome > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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>