-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 2/22/2013 3:29 PM, Johannes Weiner wrote: >> 1) It is completely useless for writing files. This hint >> should allow a program generating lots of writes to files that >> will not likely be read again to reduce the cache pressure that >> causes. > > Wouldn't direct IO make more sense in that case? It could, but doing direct aio is a lot more complicated than just using posix_fadvise. Also it has problem #3: even if it is unlikely, it *may* be used again, so it makes sense to cache it if we have plenty of ram. > Minchan worked on deactivating pages on truncation. Maybe all it > takes is to implement deactivate_mapping_range() or something to > combine a page cache walk with deactivate_page(). Looks like a good idea! > While you are at it, madvise(MADV_DONTNEED) does not do anything > to the page cache, but it probably should. :-) It seems to be implemented by discarding the pages, even if dirty. This also seems to be wrong. According to posix, this is a hint that it will not access the pages again any time *soon*, not that the data will never be needed again and so it can be discarded. It looks like MADV_SEQUENTIAL is missing the second part of its implementation: making sure the pages will be discarded soon after they are accessed. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.17 (MingW32) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBAgAGBQJRJ+i3AAoJEJrBOlT6nu759/IIAMbFAjJGmI7hkpt1GMtUfty8 n72BoygV3bDULpZ8BybJonRfiVw/ze9sVf6KhojB2dm9bvdZHl11DDGvf9Ro8OSr dcjWUQxbHzuzGtUtnUEZPOAj6Ux6cetBtmjUxjnLyJrijK+W+cEHzWnzUZXWddlo XcPe3IHNmj7YlTH+tcPevLCeTlzfFkjq/t4JXuZWmFW97MmMe5wTCScS0eiBYpHM SVVL+VJ8TPG9Hnk/9oP0RqAyg+SjshGfaqhM8mTFvS4FtMbp/gXFz8GnewxG322h ZdgwZqafiWsNeC8KitcTwKlxMU5fWFDLfHXKoFWgX2P7hVh8zJ9T6Ugi4KeaAN4= =RFzN -----END PGP SIGNATURE----- -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>