diff options
Diffstat (limited to 'mm/swapfile.c')
| -rw-r--r-- | mm/swapfile.c | 61 |
1 files changed, 56 insertions, 5 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c index 18dfccb91123..c531d2687dd0 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -613,10 +613,12 @@ new_cluster: } else if (!cluster_list_empty(&si->discard_clusters)) { /* * we don't have free cluster but have some clusters in - * discarding, do discard now and reclaim them + * discarding, do discard now and reclaim them, then + * reread cluster_next_cpu since we dropped si->lock */ swap_do_scheduled_discard(si); - *scan_base = *offset = si->cluster_next; + *scan_base = this_cpu_read(*si->cluster_next_cpu); + *offset = *scan_base; goto new_cluster; } else return false; @@ -722,6 +724,34 @@ static void swap_range_free(struct swap_info_struct *si, unsigned long offset, } } +static void set_cluster_next(struct swap_info_struct *si, unsigned long next) +{ + unsigned long prev; + + if (!(si->flags & SWP_SOLIDSTATE)) { + si->cluster_next = next; + return; + } + + prev = this_cpu_read(*si->cluster_next_cpu); + /* + * Cross the swap address space size aligned trunk, choose + * another trunk randomly to avoid lock contention on swap + * address space if possible. + */ + if ((prev >> SWAP_ADDRESS_SPACE_SHIFT) != + (next >> SWAP_ADDRESS_SPACE_SHIFT)) { + /* No free swap slots available */ + if (si->highest_bit <= si->lowest_bit) + return; + next = si->lowest_bit + + prandom_u32_max(si->highest_bit - si->lowest_bit + 1); + next = ALIGN_DOWN(next, SWAP_ADDRESS_SPACE_PAGES); + next = max_t(unsigned int, next, si->lowest_bit); + } + this_cpu_write(*si->cluster_next_cpu, next); +} + static int scan_swap_map_slots(struct swap_info_struct *si, unsigned char usage, int nr, swp_entry_t slots[]) @@ -746,7 +776,16 @@ static int scan_swap_map_slots(struct swap_info_struct *si, */ si->flags += SWP_SCANNING; - scan_base = offset = si->cluster_next; + /* + * Use percpu scan base for SSD to reduce lock contention on + * cluster and swap cache. For HDD, sequential access is more + * important. + */ + if (si->flags & SWP_SOLIDSTATE) + scan_base = this_cpu_read(*si->cluster_next_cpu); + else + scan_base = si->cluster_next; + offset = scan_base; /* SSD algorithm */ if (si->cluster_info) { @@ -835,7 +874,6 @@ checks: unlock_cluster(ci); swap_range_alloc(si, offset, 1); - si->cluster_next = offset + 1; slots[n_ret++] = swp_entry(si->type, offset); /* got enough slots or reach max slots? */ @@ -884,6 +922,7 @@ checks: } done: + set_cluster_next(si, offset + 1); si->flags -= SWP_SCANNING; return n_ret; @@ -2653,6 +2692,8 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) mutex_unlock(&swapon_mutex); free_percpu(p->percpu_cluster); p->percpu_cluster = NULL; + free_percpu(p->cluster_next_cpu); + p->cluster_next_cpu = NULL; vfree(swap_map); kvfree(cluster_info); kvfree(frontswap_map); @@ -3205,11 +3246,19 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) unsigned long ci, nr_cluster; p->flags |= SWP_SOLIDSTATE; + p->cluster_next_cpu = alloc_percpu(unsigned int); + if (!p->cluster_next_cpu) { + error = -ENOMEM; + goto bad_swap_unlock_inode; + } /* * select a random position to start with to help wear leveling * SSD */ - p->cluster_next = 1 + prandom_u32_max(p->highest_bit); + for_each_possible_cpu(cpu) { + per_cpu(*p->cluster_next_cpu, cpu) = + 1 + prandom_u32_max(p->highest_bit); + } nr_cluster = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER); cluster_info = kvcalloc(nr_cluster, sizeof(*cluster_info), @@ -3325,6 +3374,8 @@ bad_swap_unlock_inode: bad_swap: free_percpu(p->percpu_cluster); p->percpu_cluster = NULL; + free_percpu(p->cluster_next_cpu); + p->cluster_next_cpu = NULL; if (inode && S_ISBLK(inode->i_mode) && p->bdev) { set_blocksize(p->bdev, p->old_block_size); blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL); |