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Report swapinfo #140

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40 changes: 27 additions & 13 deletions qmemman/meminfo-writer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -16,17 +16,24 @@ int used_mem_change_threshold;
int delay;
int usr1_received;

const char *parse(const char *meminfo_buf, const char* dom_current_buf)
typedef struct {
char *mem;
char *swap;
} UsedMem;

UsedMem parse(const char *meminfo_buf, const char* dom_current_buf)

@marmarek marmarek Jul 10, 2026

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FWIW the usual method in C for returning more results is to either return a pointer to a structure (usually dynamically allocated via malloc), or add output parameters (pointers to where function should write result). In case of a simple structure like this, compiler will do the latter for you here, so it can stay this way, but keep in mind it wont be efficient code in more complex cases.

{
const char *ptr = meminfo_buf;
static char outbuf[4096];
static char used_mem_buf[4096];
static char used_swap_buf[4096];
long long val;
int len;
int ret;
long long MemTotal = 0, MemFree = 0, Buffers = 0, Cached = 0, SwapTotal =
0, SwapFree = 0;
unsigned long long key;
long long used_mem, used_mem_diff;
long long used_swap;
int nitems = 0;

while (nitems != (1<<6)-1 || !*ptr) {
Expand Down Expand Up @@ -68,7 +75,8 @@ const char *parse(const char *meminfo_buf, const char* dom_current_buf)
used_mem =
MemTotal - Buffers - Cached - MemFree + SwapTotal - SwapFree;
if (used_mem < 0)
return NULL;
return (UsedMem){ .mem = NULL, .swap = NULL };
used_swap = SwapTotal - SwapFree;

used_mem_diff = used_mem - prev_used_mem;
if (used_mem_diff < 0)
Expand All @@ -78,10 +86,13 @@ const char *parse(const char *meminfo_buf, const char* dom_current_buf)
|| (used_mem > prev_used_mem && used_mem / 10 > (MemTotal+12) / 13
&& used_mem_diff > used_mem_change_threshold/2)) {
prev_used_mem = used_mem;
sprintf(outbuf, "%lld", used_mem);
return outbuf;
sprintf(used_mem_buf, "%lld", used_mem);
sprintf(used_swap_buf, "%lld", used_swap);
Comment on lines +89 to +90

@marmarek marmarek Jul 10, 2026

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Redundant calls.

snprintf(used_mem_buf, sizeof used_mem_buf, "%lld", used_mem);
snprintf(used_swap_buf, sizeof used_swap_buf, "%lld", used_swap);
return (UsedMem){ .mem = used_mem_buf, .swap = used_swap_buf };
}
return NULL;
return (UsedMem){ .mem = NULL, .swap = NULL };

@ben-grande ben-grande Jul 13, 2026

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Report swap change if above threshold despite memory being below its threshold.

}

void usage(void)
Expand All @@ -94,10 +105,14 @@ void usage(void)
exit(1);
}

void send_to_qmemman(struct xs_handle *xs, const char *data)
void send_to_qmemman(struct xs_handle *xs, const char *mem, const char *swap)
{
if (!xs_write(xs, XBT_NULL, "memory/meminfo", data, strlen(data))) {
syslog(LOG_DAEMON | LOG_ERR, "error writing xenstore ?");
if (!xs_write(xs, XBT_NULL, "memory/meminfo", mem, strlen(mem))) {
syslog(LOG_DAEMON | LOG_ERR, "error writing meminfo to xenstore ?");
exit(1);
}
if (!xs_write(xs, XBT_NULL, "memory/swapinfo", swap, strlen(swap))) {

@marmarek marmarek Jul 10, 2026

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Note to self: this can be merged only after core-admin part, which sets necessary xenstore access.

syslog(LOG_DAEMON | LOG_ERR, "error writing swapinfo to xenstore ?");
exit(1);
}
}
Expand All @@ -121,7 +136,6 @@ static void update(struct xs_handle *xs, int meminfo_fd, int dom_current_fd)
char dom_current_buf[32];
char dom_current_buf2[32];
char meminfo_buf[4096];
const char *meminfo_data;

pread0_string(dom_current_fd, dom_current_buf, sizeof(dom_current_buf));

Expand All @@ -140,9 +154,9 @@ static void update(struct xs_handle *xs, int meminfo_fd, int dom_current_fd)
break;
}

meminfo_data = parse(meminfo_buf, dom_current_buf);
if (meminfo_data)
send_to_qmemman(xs, meminfo_data);
UsedMem meminfo_data = parse(meminfo_buf, dom_current_buf);
if (meminfo_data.mem && meminfo_data.mem[0])

@ben-grande ben-grande Jul 13, 2026

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https://github.com/QubesOS/qubes-linux-utils/pull/140/changes#r3569568589

send_to_qmemman(xs, meminfo_data.mem, meminfo_data.swap);
}

int main(int argc, char **argv)
Expand Down