mirror of
https://github.com/schoebel/mars
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c319230fa1
Dastically boost random write performance on RAID controllers with BBUs. Writeback is only performed when there is no IO contention / starvation. The old IO contention controller was suited to workstations. Now server loads are well-controlled even when BBUs are present.
79 lines
1.5 KiB
C
79 lines
1.5 KiB
C
// (c) 2010 Thomas Schoebel-Theuer / 1&1 Internet AG
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// (c) 2012 Thomas Schoebel-Theuer
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//#define BRICK_DEBUGGING
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//#define MARS_DEBUGGING
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//#define IO_DEBUGGING
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include "mars.h"
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#include "lib_rank.h"
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void ranking_compute(struct rank_data *rkd, const struct rank_info rki[], int x)
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{
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int i;
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for (i = 0; ; i++) {
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int x0 = rki[i].rki_x;
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int x1;
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int y0;
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int y1;
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int points;
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if (x0 == RKI_DUMMY)
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break;
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if (x < x0)
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continue;
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x1 = rki[i+1].rki_x;
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if (x1 == RKI_DUMMY)
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break;
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y0 = rki[i].rki_y;
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y1 = rki[i+1].rki_y;
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// linear interpolation
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points = ((long long)(x - x0) * (long long)(y1 - y0)) / (x1 - x0) + y0;
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MARS_IO("i = %d x0 = %d x1 = %d y0 = %d y1 = %d points = %d\n", i, x0, x1, y0, y1, points);
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rkd->rkd_tmp += points;
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break;
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}
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}
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EXPORT_SYMBOL_GPL(ranking_compute);
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int ranking_select(struct rank_data rkd[], int rkd_count)
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{
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int res = -1;
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int max = INT_MIN / 2;
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int i;
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MARS_IO("rkd_count = %d\n", rkd_count);
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for (i = 0; i < rkd_count; i++) {
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struct rank_data *tmp = &rkd[i];
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int rest = tmp->rkd_current_points;
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if (rest <= 0)
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continue;
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//rest -= tmp->rkd_got;
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if (rest > max) {
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max = rest;
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res = i;
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}
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}
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/* Prevent underflow in the long term
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* and reset the "clocks" after each round of
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* weighted round-robin selection.
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*/
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if (max < 0 && res >= 0) {
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for (i = 0; i < rkd_count; i++)
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rkd[i].rkd_got += max;
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}
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MARS_IO("res = %d\n", res);
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return res;
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}
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EXPORT_SYMBOL_GPL(ranking_select);
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