SDL2 texture update speed

I'm trying to setup SDL2 environment for future running software rendering examples, so i need direct access to pixels to draw. Here is some code, that draws 1 red pixel to texture, then displaying a it said https://wiki.libsdl.org/MigrationGuide#If_your_game_just_wants_to_get_fully-rendered_frames_to_the_screen

#include <SDL.h>
#include <stdio.h>

const int SCREEN_WIDTH = 1920;
const int SCREEN_HEIGHT = 1080;

SDL_Window* gWindow;
SDL_Renderer* gRenderer;
SDL_Texture* gTexture;
SDL_Event e;

void* gPixels = NULL;
int gPitch = SCREEN_WIDTH * 4;

bool gExitFlag = false;

Uint64 start;
Uint64 end;
Uint64 freq;
double seconds;

int main(int argc, char* args[])
{
    SDL_Init(SDL_INIT_VIDEO);
    gWindow = SDL_CreateWindow("SDL Tutorial", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN | SDL_WINDOW_OPENGL);
    gRenderer = SDL_CreateRenderer(gWindow, -1, SDL_RENDERER_ACCELERATED); // | SDL_RENDERER_PRESENTVSYNC); vsync is turned off
    gTexture = SDL_CreateTexture(gRenderer, SDL_PIXELFORMAT_RGBA8888, SDL_TEXTUREACCESS_STREAMING, SCREEN_WIDTH, SCREEN_HEIGHT);

    while (!gExitFlag)
    {
        while (SDL_PollEvent(&e) != 0)
        {
            if (e.type == SDL_QUIT)
            {
                gExitFlag = true;
            }
        }

        start = SDL_GetPerformanceCounter();

        SDL_LockTexture(gTexture, NULL, &gPixels, &gPitch);
        *((uint32_t*)gPixels) = 0xff000ff;
        SDL_UnlockTexture(gTexture); //20-100ms on different hardware

        end = SDL_GetPerformanceCounter();
        freq = SDL_GetPerformanceFrequency();

        SDL_RenderCopy(gRenderer, gTexture, NULL, NULL);
        SDL_RenderPresent(gRenderer);

        gPixels = NULL;
        gPitch = 0;

        seconds = (end - start) / static_cast<double>(freq);
        printf("Frame time: %fms\n", seconds * 1000.0);
    }

    SDL_DestroyWindow(gWindow);
    SDL_DestroyRenderer(gRenderer);
    SDL_DestroyTexture(gTexture);

    SDL_Quit();
    return 0;
}

As i mention in the code comment SDL_UnlockTexture gets up to 100ms with fullhd texture. (Switching to SDL_UpdateTexture cause no significant difference) It is too much for realtime rendering i think. Am i doing something wrong or i should not use at all texture API(or any other GPU-accelerated api, where texture must be uploaded to gpu memory every frame) for realtime rendering whole frame?