Attachment 185184 Details for Bug 221356 – Improve swapon_check_swzone() function

[patch] Improve swapon_check_swzone() function

swap_pager.diff (text/plain), 3.81 KB, created by ota on 2017-08-09 05:22:20 UTC

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Creator: ota

Created: 2017-08-09 05:22:20 UTC

Size: 3.81 KB

patch

obsolete

>Improve swapon_check_swzone() function.
>
>Change to more descriptive swapon_check_swzone() warnings.
>#1 Indicate half the size is recommended size.
>(I couldn't figure out and don't know why half is recommended, though.)
>#2 Advice when the swap device size exceeds the max size.
>
>Convert swap_pager_full to static variable as it is not used in global space.
>Add a unit to swap_total description.
>Call uma_zone_get_max() to find proper swap_maxpages.
>Use swap_maxpages and other global variable in swapon_check_swzone().
>Convert swapon_check_swzone() to a void function.
>
>Index: vm/swap_pager.c
>===================================================================
>--- vm/swap_pager.c	(revision 321376)
>+++ vm/swap_pager.c	(working copy)
>@@ -155,7 +156,7 @@
> 
> static vm_ooffset_t swap_total;
> SYSCTL_QUAD(_vm, OID_AUTO, swap_total, CTLFLAG_RD, &swap_total, 0,
>-    "Total amount of available swap storage.");
>+    "Total bytes of all swap storages.");
> static vm_ooffset_t swap_reserved;
> SYSCTL_QUAD(_vm, OID_AUTO, swap_reserved, CTLFLAG_RD, &swap_reserved, 0,
>     "Amount of swap storage needed to back all allocated anonymous memory.");
>@@ -315,7 +316,7 @@
> #define SWM_FREE	0x02	/* free, period			*/
> #define SWM_POP		0x04	/* pop out			*/
> 
>-int swap_pager_full = 2;	/* swap space exhaustion (task killing) */
>+static int swap_pager_full = 2;	/* swap space exhaustion (task killing) */
> static int swap_pager_almost_full = 1; /* swap space exhaustion (w/hysteresis)*/
> static int nsw_rcount;		/* free read buffers			*/
> static int nsw_wcount_sync;	/* limit write buffers / synchronous	*/
>@@ -550,6 +558,7 @@
> 		 */
> 		n -= ((n + 2) / 3);
> 	} while (n > 0);
>+	n = uma_zone_get_max(swap_zone);
> 	if (n2 != n)
> 		printf("Swap zone entries reduced from %lu to %lu.\n", n2, n);
> 	swap_maxpages = n * SWAP_META_PAGES;
>@@ -2108,27 +2135,39 @@
> 
> /*
>  * Check that the total amount of swap currently configured does not
>- * exceed half the theoretical maximum.  If it does, print a warning
>- * message and return -1; otherwise, return 0.
>+ * exceed half or full of the maximum.  If it does, print a warning
>+ * message accordingly.
>  */
>-static int
>-swapon_check_swzone(unsigned long npages)
>+static void
>+swapon_check_swzone()
> {
>-	unsigned long maxpages;
>+	unsigned long npages = swap_total / PAGE_SIZE;
> 
>-	/* absolute maximum we can handle assuming 100% efficiency */
>-	maxpages = uma_zone_get_max(swap_zone) * SWAP_META_PAGES;
>+	printf("swap_pager_avail=%d and swap_maxpages=%lu\n",
>+		swap_pager_avail, swap_maxpages);
> 
>+	if (npages <= swap_maxpages / 2) {
>+		return;
>+	}
>+	/* we exceeded maximum and won't be able to use extra pages */
>+	else if (npages > swap_maxpages) {
>+		printf("warning: total configured swap (%lu pages) "
>+		    "exceeds maximum amount (%lu pages).\n",
>+		    npages, swap_maxpages);
>+		printf("%d devices will be used in round-robin but "
>+		    "%lu pages will not be used\n",
>+		    nswapdev, npages - swap_maxpages);
>+		return;
>+	}
> 	/* recommend using no more than half that amount */
>-	if (npages > maxpages / 2) {
>+	else {
> 		printf("warning: total configured swap (%lu pages) "
> 		    "exceeds maximum recommended amount (%lu pages).\n",
>-		    npages, maxpages / 2);
>+		    npages, swap_maxpages / 2);
> 		printf("warning: increase kern.maxswzone "
> 		    "or reduce amount of swap.\n");
>-		return (-1);
>+		return;
> 	}
>-	return (0);
> }
> 
> static void
>@@ -2196,7 +2235,7 @@
> 	nswapdev++;
> 	swap_pager_avail += nblks - 2;
> 	swap_total += (vm_ooffset_t)nblks * PAGE_SIZE;
>-	swapon_check_swzone(swap_total / PAGE_SIZE);
>+	swapon_check_swzone();
> 	swp_sizecheck();
> 	mtx_unlock(&sw_dev_mtx);
> }
>Index: vm/swap_pager.h
>===================================================================
>--- vm/swap_pager.h	(revision 321376)
>+++ vm/swap_pager.h	(working copy)
>@@ -73,7 +73,6 @@
> 
> #ifdef _KERNEL
> 
>-extern int swap_pager_full;
> extern int swap_pager_avail;
> 
> struct xswdev;

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Attachments on bug 221356: 185184 | 187070 | 187071