On 10/26/2012 02:58 PM, Fengguang Wu wrote:
static void shrink_readahead_size_eio(struct file *filp, struct file_ra_state *ra) { - ra->ra_pages /= 4; + spin_lock(&filp->f_lock); + filp->f_mode |= FMODE_RANDOM; + spin_unlock(&filp->f_lock); As the example in comment above this function, the read maybe still sequential, and it will waste IO bandwith if modify to FMODE_RANDOM directly.Yes immediately disabling readahead may hurt IO performance, the original '/ 4' may perform better when there are only 1-3 IO errors encountered.
Hi Fengguang, Why the number should be 1-3? Regards, Chen
Thanks, Fengguang -- 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>
-- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
