summaryrefslogtreecommitdiffstats
path: root/lib/bitmap.c
diff options
context:
space:
mode:
authorPaul Gortmaker <paul.gortmaker@windriver.com>2021-02-21 03:08:25 -0500
committerPaul E. McKenney <paulmck@kernel.org>2021-03-08 14:16:58 -0800
commit2c4885d24e64941702a8f81c8e83289823ba35d0 (patch)
treee873dad739f3b0f531c38d580ef46423ec79edf1 /lib/bitmap.c
parentf3c869caef648c541a7445f2a6ba2196d343f542 (diff)
downloadlinux-2c4885d24e64941702a8f81c8e83289823ba35d0.tar.bz2
lib: bitmap: support "N" as an alias for size of bitmap
While this is done for all bitmaps, the original use case in mind was for CPU masks and cpulist_parse() as described below. It seems that a common configuration is to use the 1st couple cores for housekeeping tasks. This tends to leave the remaining ones to form a pool of similarly configured cores to take on the real workload of interest to the user. So on machine A - with 32 cores, it could be 0-3 for "system" and then 4-31 being used in boot args like nohz_full=, or rcu_nocbs= as part of setting up the worker pool of CPUs. But then newer machine B is added, and it has 48 cores, and so while the 0-3 part remains unchanged, the pool setup cpu list becomes 4-47. Multiple deployment becomes easier when we can just simply replace 31 and 47 with "N" and let the system substitute in the actual number at boot; a number that it knows better than we do. Cc: Yury Norov <yury.norov@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Suggested-by: Yury Norov <yury.norov@gmail.com> # move it from CPU code Acked-by: Yury Norov <yury.norov@gmail.com> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'lib/bitmap.c')
-rw-r--r--lib/bitmap.c22
1 files changed, 17 insertions, 5 deletions
diff --git a/lib/bitmap.c b/lib/bitmap.c
index 833f152a2c43..9f4626a4c95f 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -519,11 +519,17 @@ static int bitmap_check_region(const struct region *r)
return 0;
}
-static const char *bitmap_getnum(const char *str, unsigned int *num)
+static const char *bitmap_getnum(const char *str, unsigned int *num,
+ unsigned int lastbit)
{
unsigned long long n;
unsigned int len;
+ if (str[0] == 'N') {
+ *num = lastbit;
+ return str + 1;
+ }
+
len = _parse_integer(str, 10, &n);
if (!len)
return ERR_PTR(-EINVAL);
@@ -571,7 +577,9 @@ static const char *bitmap_find_region_reverse(const char *start, const char *end
static const char *bitmap_parse_region(const char *str, struct region *r)
{
- str = bitmap_getnum(str, &r->start);
+ unsigned int lastbit = r->nbits - 1;
+
+ str = bitmap_getnum(str, &r->start, lastbit);
if (IS_ERR(str))
return str;
@@ -581,7 +589,7 @@ static const char *bitmap_parse_region(const char *str, struct region *r)
if (*str != '-')
return ERR_PTR(-EINVAL);
- str = bitmap_getnum(str + 1, &r->end);
+ str = bitmap_getnum(str + 1, &r->end, lastbit);
if (IS_ERR(str))
return str;
@@ -591,14 +599,14 @@ static const char *bitmap_parse_region(const char *str, struct region *r)
if (*str != ':')
return ERR_PTR(-EINVAL);
- str = bitmap_getnum(str + 1, &r->off);
+ str = bitmap_getnum(str + 1, &r->off, lastbit);
if (IS_ERR(str))
return str;
if (*str != '/')
return ERR_PTR(-EINVAL);
- return bitmap_getnum(str + 1, &r->group_len);
+ return bitmap_getnum(str + 1, &r->group_len, lastbit);
no_end:
r->end = r->start;
@@ -625,6 +633,10 @@ no_pattern:
* From each group will be used only defined amount of bits.
* Syntax: range:used_size/group_size
* Example: 0-1023:2/256 ==> 0,1,256,257,512,513,768,769
+ * The value 'N' can be used as a dynamically substituted token for the
+ * maximum allowed value; i.e (nmaskbits - 1). Keep in mind that it is
+ * dynamic, so if system changes cause the bitmap width to change, such
+ * as more cores in a CPU list, then any ranges using N will also change.
*
* Returns: 0 on success, -errno on invalid input strings. Error values:
*