* Scan for pages at adjacent offsets within the given page's object that are * eligible for laundering, form a cluster of these pages and the given page, * and launder that cluster. */
| 348 | * and launder that cluster. |
| 349 | */ |
| 350 | static int |
| 351 | vm_pageout_cluster(vm_page_t m) |
| 352 | { |
| 353 | vm_object_t object; |
| 354 | vm_page_t mc[2 * vm_pageout_page_count], p, pb, ps; |
| 355 | vm_pindex_t pindex; |
| 356 | int ib, is, page_base, pageout_count; |
| 357 | |
| 358 | object = m->object; |
| 359 | VM_OBJECT_ASSERT_WLOCKED(object); |
| 360 | pindex = m->pindex; |
| 361 | |
| 362 | vm_page_assert_xbusied(m); |
| 363 | |
| 364 | mc[vm_pageout_page_count] = pb = ps = m; |
| 365 | pageout_count = 1; |
| 366 | page_base = vm_pageout_page_count; |
| 367 | ib = 1; |
| 368 | is = 1; |
| 369 | |
| 370 | /* |
| 371 | * We can cluster only if the page is not clean, busy, or held, and |
| 372 | * the page is in the laundry queue. |
| 373 | * |
| 374 | * During heavy mmap/modification loads the pageout |
| 375 | * daemon can really fragment the underlying file |
| 376 | * due to flushing pages out of order and not trying to |
| 377 | * align the clusters (which leaves sporadic out-of-order |
| 378 | * holes). To solve this problem we do the reverse scan |
| 379 | * first and attempt to align our cluster, then do a |
| 380 | * forward scan if room remains. |
| 381 | */ |
| 382 | more: |
| 383 | while (ib != 0 && pageout_count < vm_pageout_page_count) { |
| 384 | if (ib > pindex) { |
| 385 | ib = 0; |
| 386 | break; |
| 387 | } |
| 388 | if ((p = vm_page_prev(pb)) == NULL || |
| 389 | vm_page_tryxbusy(p) == 0) { |
| 390 | ib = 0; |
| 391 | break; |
| 392 | } |
| 393 | if (vm_page_wired(p)) { |
| 394 | ib = 0; |
| 395 | vm_page_xunbusy(p); |
| 396 | break; |
| 397 | } |
| 398 | vm_page_test_dirty(p); |
| 399 | if (p->dirty == 0) { |
| 400 | ib = 0; |
| 401 | vm_page_xunbusy(p); |
| 402 | break; |
| 403 | } |
| 404 | if (!vm_page_in_laundry(p) || !vm_page_try_remove_write(p)) { |
| 405 | vm_page_xunbusy(p); |
| 406 | ib = 0; |
| 407 | break; |
no test coverage detected