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
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