6ba6f5f6a
Denys Vlasenko
2026-01-18
Subject
vmstat: reduce the chances of misaligned columns
Binary
No binary (build failed)
Architecture & Compiler Flags
gcc -Wp,-MD,applets/.usage.d -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer -Iinclude -Iinclude -o applets/usage applets/usage.c
Build Log
(log yok)
Commit Diff GitHub →
procps/vmstat.c+26 -8
| @@ -337,8 +337,9 @@ static void print_row(const unsigned data[NCOLS], | |
| unsigned i; | |
| bool is_first; | |
| unsigned percent_sum = 0; | |
| + | int overrun; |
| - | for (coli = coldescs, i = 0; next_col(&col, &coli); i++) |
| + | for (coli = coldescs, i = 0; next_col(&col, &coli); i++) { |
| if (col.mod & MOD_PERCENT) { | |
| unsigned value = data[i]; | |
| if (col.mod & MOD_DELTA) { | |
| @@ -351,7 +352,9 @@ static void print_row(const unsigned data[NCOLS], | |
| } | |
| percent_sum += value; | |
| } | |
| + | } |
| + | overrun = 0; |
| is_first = 1; | |
| for (coli = coldescs, i = 0; next_col(&col, &coli); i++) { | |
| unsigned value = data[i]; | |
| @@ -368,14 +371,29 @@ static void print_row(const unsigned data[NCOLS], | |
| } | |
| if ((col.mod & MOD_DECREMENT) && value) | |
| value--; | |
| - | //FIXME: memory can easily overflow the columns: |
| - | // r b swpd free buff cache si so bi bo in cs us sy id wa st gu |
| - | // 3 0 0 2019152 1029788 8602060 0 0 29 211 5699 13 9 5 86 0 0 0 //CURRENT CODE:BAD |
| - | // 3 0 0 2019152 1029788 8602060 0 0 29 211 5699 13 9 5 86 0 0 0 //SMARTER |
| - | //FIXME: cs (context switches) easily overflow too |
| - | printf(" %*u" + is_first, col.width, value); |
| - | is_first = 0; |
| + | |
| + | /* memory can easily overflow the columns: |
| + | * r b swpd free buff cache si so bi bo in cs us sy id wa st gu |
| + | * 3 0 0 2019152 1029788 8602060 0 0 29 211 5699 13 9 5 86 0 0 0 |
| + | * ^ ^ ^ shortened width was here |
| + | * To improve this, shorten the requested field width if previous field overflowed. |
| + | */ |
| + | { |
| + | int digits_printed, width; |
| + | width = (col.width - overrun >= 0 ? col.width - overrun : 0); |
| + | digits_printed = printf(" %*u" + is_first, width, value) - 1 + is_first; |
| + | overrun += (digits_printed - col.width); |
| + | is_first = 0; |
| + | //TODO: more improvements: |
| + | //Shift left entire set of memory fields if it is space-padded at the left and overruns at the right, |
| + | //as in the example above (zero bytes in swap). |
| + | //For large intervals such as "vmstat 60" (one minute), |
| + | //can use smart_ulltoa4() to format "si", "so", "in" and "cs"; |
| + | //smart_ulltoa5() to format "bi" and "bo": |
| + | //this way, we can show arbitrarily large accumucated counts for these. |
| + | } |
| } | |
| + | |
| bb_putchar('\n'); | |
| } | |